Dotnet Development

C# and VB Basics
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DRAFT

C# and VB Basics

All examples assume the target framework .NET 6(net6.0) unless otherwise stated in a particular section.

Variables

Variables are the basic working blocks in code. You use variables to hold values. There are several different variable types but in this lesson we will cover only four of them.

To declare a variable you use the language keyword “Dim” used with a name and “As”. So if you want a string called “Hello World” named TestVariable you would declare it like this.

Dim TestVariable As String = "Hello World"

string TestVariable = "Hello World";

This example declares a variable and assigns a value at the same time. However you can declare a variable without assigning value. The value can always be assigned later. A good general rule is only declare a variable when it is ready to be used (assigned) when possible.

Integer - are like whole numbers but can contain negatives
String - contain multiple characters
Decimal - numbers with decimals
Boolean - is true or false

Integers

Integers are like whole numbers but can contain negatives. So they have negatives, zero, or positives.

For example -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5 are all integer values.

To declare an integer you can do this.

Dim i As Integer

int i;

This example creates a new variable of type Integer name i. It does not assign any value to i. To assign a value to i you can do it like this.

i=1

i=1;

Now the value of i is 1.

i=2

i=2;

Now the value of i is 2.

Strings

Strings can hold any value. They can have letters, numbers, special characters. They can be long or short

To declare a string you can do this.

Dim s As String

string s;

This example creates an empty string called s. This string has no value

To assign the value “hello world” to the variable s we would do.

s = "hello world"

s = "hello world";

The value of the variable can be reassigned at any time so if we want to change the value to “purple monkey dishwasher” just do the same as above put with the new string.

s = "purple monkey dishwasher"

s = "purple monkey dishwasher";

If we want to see the value of a variable printed to the console we can write.

System.Console.WriteLine("The value of s is: " & s)

System.Console.WriteLine($"The value of s is: {s}");

We see here that s is value is append to the string “The value of s is: “ and then printed to the console as “The value of s is: purple monkey dishwasher”. You can append any string to any other string at any time using the & symbol.

StringBuilder

If you are appending to a string again and again or changing it value over and over again this can become very slow. String operations like this can be speed up using the StringBuilder class.

To use a string builder you need to initialize System.Text.StringBuilder.

Dim builder As New System.Text.StringBuilder
builder.Append("Hello World ")
builder.Append("Peter.  ")
builder.Append("Have a good day.")

System.Console.WriteLine(builder.ToString)

var builder = new System.Text.StringBuilder();
builder.Append("Hello World ");
builder.Append("Peter.  ");
builder.Append("Have a good day.");

System.Console.WriteLine(builder.ToString());

This will print “Hello World Peter. Have a good day.”.

What this does is keep adding to a buffer and when you call the ToString method it finally creates a string. This is much faster then concatenating the string together like the following.

System.Console.WriteLine("Hello World " & "Peter.  " & "Have a good day.")

System.Console.WriteLine("Hello World " + "Peter.  " + "Have a good day.");

This example probably is not faster since it is so tiny but if you did this with 100 000 strings the string builder would be much faster.

Decimals

Decimals are used when you need numeric values that contain decimals places. It is essential if you are doing financial calculations that you use decimals and no other data type. Do not use doubles.

For example -5.32, -4.76, -3.7654, -2.1, -1.343, 0.13, 1.786555, 2.2, 3.765, 4.22, 5.3446 are all decimal values.

To declare a decimal you can do this.

Dim d As Decimal = 4.444D

decimal d = 4.444m;

This example creates a new variable of type Decimal with the name d and a value of 4.444d

To assign a new value to d you can do it like this.

d=5.437D

d = 5.437m;

Now the value of d is 5.437.

d=2.55

d = 2.55m;

Now the value of d is 2.55. As shown above variables in function can always be reassigned new values

Booleans

Booleans are variables that can be either True or False. That is all they hold. Booleans default to false.

To declare a boolean you can do this.

Dim b As Boolean = False

bool b = false;

This example creates a new variable of type Boolean named b. It does not assign any value to b. To assign a value to b you can do it like this.

b=True

b=true;

Now the value of b is True.

b=False

b=false;

Now the value of b is False.

There is no other value that a boolean can hold. If you do not set a value a boolean will default to False.

Chars

Chars are variables that can hold one character and only one character. It can be any character available but only one character at a time.

To declare a char you do this.

Dim c As Char

char c;

This example creates a new variable of type Char named c. It does not assign any value to c. To assign a value to c you can do it like this.

c="A"c

c='A';

Now the value of c is A.

c="~"c

c='~';

Now the value of c is ~.

As is written above any character can be held in a char variable but only one character at a time. Like any other variable type you can print the variable to the console using like this.

System.Console.WriteLine(c)

System.Console.WriteLine(c);

DateTime

DateTime variables can hold a date and time value. If you just want a date you can also use Date instead of DateTime.

To declare a DateTime you do this.

Dim t As DateTime

DateTime t;

This example creates a new variable of type DateTime named t. It does not assign any value to t. To assign a value to t you can do it like this.

t = DateTime.Now

t = DateTime.Now;

This assigns the current date and time to the variable t.

If you want to assign a specific date such as 01 may 2012, do it like this.

t = New DateTime(2012, 5, 1)

t = new DateTime(2012, 5, 1);

Now the date of t would now be 01 May 2012 with a time of 00:00:00.

If you want to print the date to the console you can use several of its functions to print in different formats.

System.Console.WriteLine(t.ToString)
System.Console.WriteLine(t.ToShortDateString)

System.Console.WriteLine(t.ToString());
System.Console.WriteLine(t.ToShortDateString());

There are several other functions that can be looked up and used but generally I find these are the two that I use most often.

Doubles

Doubles are variables that hold numeric values with decimal places. They are similar to the decimal variable type but are less accurate and accumulate rounding errors when calculations are performed.

To declare a double you do this.

Dim d As Double

double d;

This example creates a new variable of type Double named d. It does not assign any value to d. To assign a value to d you can do it like this.

d = 5.555567

d = 5.555567;

Now the value of d is 5.555567.

d = 2.1

d = 2.1;

Now the value of d is 2.1.

Like any other variable type you can print the variable to the console using like this.

System.Console.WriteLine(d)

System.Console.WriteLine(d);

Objects

Objects are a base type that all other objects are derived from. This means that any other variable no matter the type can be assigned to an object.

To declare an object you do this.

Dim o As Object

Object o;

This example creates a new variable of type Object named o. It does not assign any value to o. To assign a value to o you can do it like this.

o = "A"c

o = 'A';

Now the value of o is A. The type is Char stored in the object. If we assign an integer.

o = 120

o = 120;

Now the value of o is 120 and the type of the stored value is an Integer

We can do the same by assigning strings, decimals, doubles, or any other type or object into an object of type Object.

If we print the object when assigned an integer it will print the integer. If we print when it is assigned char it will print the char and so on with the other variable types.

System.Console.WriteLine(o)

System.Console.WriteLine(o);

Generally I suggest avoiding the Object type as it defeats type checking that a compiler does and in my experience causes a lot of run time errors. The runtime errors are caused when code attempts to do an operation on the object that is not supported by the stored variable type. If we declare the type we want to use in code the compiler can do all the checks that are needed when the program is complied.

Objects

VB and c# have built in types such as int, bool, string, and others. Now it is time to create types that is more specific to your application

For example if you are writing an application about tv channels/stations you probably do not want to use strings and integers. It will be easier to think about stations and channels. In VB, c#, and other object oriented languages we can define our own types and use them just like the built in types.

To use a class you must declare one as you would any other variable type. I will be using the word class and object interchangeably.

For example you declare an integer like this

Dim i As Integer = 0

int i = 0;

Below we create our own data type using the keyword Class. The best way to use a class is to think of it as an object. For the purpose of this example our object is going to be a tv show. Tv shows have many different aspects to them so we create an object that represent them.

Included in the class are a new class property (ShowName) as Public and a Private variable (_showName) that the property works with. Never declare a class variable as public. Always use a property or a function. I will not explain it here but I do encourage you to read some books on object oriented design.

Private variables are accessible from any function in the class but cannot be accessed from other classes.

Public Class TVShow
    Public Sub New()
        ' constructor
    End Sub

    Private _showName As String
    ' Public properties can be accessed from any function inside the
    ' class as well as other classes
    Public Property ShowName() As String
        Get
            ' Inside the get part the private variable is returned.
            ' You can do anything you want here such as data validation
            ' before returning the data if you need or want.
            Return _showName
        End Get
        Set(ByVal value As String)
            ' Inside the set part the private variable is set.
            ' You can do anything you want here such as data validation
            ' before the data is set.
            If value.Trim = "" Then
                Throw New Exception("ShowName cannot be empty")
            End If
            _showName = value
        End Set
    End Property

    ' The above property is long form.  A shorter form can be done as seen below
    Public ReadOnly Property ShowLength As Integer
    Public ReadOnly Property Summary As String
    Public ReadOnly Property Rating As Decimal
    Public ReadOnly Property Episode As String
End Class

public class TVShow
{
    public TVShow()
    {
    }

    private string _showName;
    // Public properties can be accessed from any function inside the
    // class as well as other classes
    public string ShowName
    {
        get
        {
            // Inside the get part the private variable is returned.
            // You can do anything you want here such as data validation
            // before returning the data if you need or want.
            return _showName;
        }
        set
        {
            // Inside the set part the private variable is set.
            // You can do anything you want here such as data validation
            // before the data is set.
            if (value.Trim() == "")
                throw new Exception("ShowName cannot be empty");
            _showName = value;
        }
    }

    // The above property is long form.  A shorter form can be done as seen below
    public int ShowLength {get; init;}
    public string Summary {get; init;}
    public decimal Rating {get; init;}
    public string Episode {get; init;}
}

You create a new instance of a class the same way you would with an Integer. You create a new instance like this

Dim starTrek As New TVShow With {
    .ShowName = "Star Trek"
    .ShowLength = 1380
    .Summary = "Teleport Disaster"
    .Rating = 5.0D
    .Episode = "1x12"
}

var starTrek = new TVShow() {
    ShowName = "Star Trek",
    ShowLength = 1380,
    Summary = "Teleport Disaster",
    Rating = 5.0m,
    Episode = "1x12"
};

If you want a second object you just declare another one.

Dim dexter As New TVShow With {
    .ShowName = "Dexter"
    .ShowLength = 1380
    .Summary = "Dexter kills again."
    .Rating = 4.8D
    .Episode = "10x01"
}

var dexter = new TVShow() {
    ShowName = "Dexter",
    ShowLength = 1380,
    Summary = "Dexter kills again.",
    Rating = 4.8D,
    Episode = "10x01"
};

Methods

Methods, also known as functions, are used to break code apartment into smaller chunks. Functions should do one task and do it well. Functions can be called again and again. They are used to keep duplicate code from building up. This makes things easier to understand. They can be chained/used together to perform complex tasks.

Functions can return a value or return no value. In vb functions that return a value use the key word Function and ones that do not return a value use the keyword Sub. In c# functions that return a value have a type such as a built-in type or object and functions that do not return a value use the keyword *void.

public class TVShow
{
    public string ShowName {get; init;}
    public int ShowLength {get; init;}
    public string Summary {get; init;}
    public decimal Rating {get; init;}
    public string Episode {get; init;}

    // includeSummary is a method parameter
    public void PrettyPrint(bool includeSummary){
        if (includeSummary)
        {
            Console.WriteLine($"{ShowName} {Episode} {Rating} {ShowLength} {Summary}");
        }
        else
        {
            Console.WriteLine($"{ShowName} {Episode} {Rating} {ShowLength}");
        }
    }

    public bool IsGoodRating(){
        return Rating >= 3.0m;
    }
}

var dexter = new TVShow() {
    ShowName = "Dexter",
    ShowLength = 1380,
    Summary = "Dexter kills again.",
    Rating = 4.8D,
    Episode = "10x01"
};

dexter.PrettyPrint(includeSummary: true);

if(dexter.IsGoodRatting()){
    Console.WriteLine("Let's watch this episode.");
}

Method and function parameters are passed by reference for objects and by value for simple types.

Interfaces

Interfaces - define behavior for multiple types. An interface contains definitions for a group of related functionalities that a non-abstract class or a struct must implement.

Interfaces in c# and vb is a way to specify what an object implements. It provides the ability to have different concrete class implementations and choose different ones at runtime.

A good example for further self study is the Microsoft ILogger.

We will build upon the TVShows class. We will define an interface. We will include a new property ParentalGuide.

Much of this will not make sense until the IOC and Depednacy injection sections later in this guide.

The following code example defines an interface named TVShow. It is not necessary or necessarily recommended to prepend the name with an I but it is very common to see such interfaces in the c# and vb world. In code bases that do prepend an I the name would be ITVShow. The following code examples will not follow that pattern.

Imagine we have a large program involving tv shows. We could pass around the instances of TVShow but that will make our program brittle if and when we need to make changes.

public interface TVShow
{
    string ShowName {get; init;}
    int ShowLength {get; init;}
    string Summary {get; init;}
    decimal Rating {get; init;}
    string Episode {get; init;}
    string ParentalGuide {get; init;}

    void PrettyPrint(bool includeSummary);
    bool IsGoodRating();
}

An interface is not initalizeable. If we were to try to do so it would be a compile time error.

// Will not compile. 
var inst = new TVShow();

Below a new class called ComedyShow implments TVShow. Notice line one with : TVShow after the class name. ComedyShow is a type of TVShow. Next notice that AdventureShow also implements TVShow.

public class ComedyShow : TVShow
{
    public string ShowName {get; init;}
    public int ShowLength {get; init;}
    public string Summary {get; init;}
    public decimal Rating {get; init;}
    public string Episode {get; init;}
    public string ParentalGuide {get; init;}

    // includeSummary is a method parameter
    public void PrettyPrint(bool includeSummary){
        if (includeSummary)
        {
            Console.WriteLine($"Comedy: {ShowName} {Episode} {Rating} {ShowLength} {Summary}");
        }
        else
        {
            Console.WriteLine($"Comedy: {ShowName} {Episode} {Rating} {ShowLength}");
        }
    }

    public bool IsGoodRating(){
        return Rating >= 3.0m;
    }
}

public class AdventureShow : TVShow
{
    public string ShowName {get; init;}
    public int ShowLength {get; init;}
    public string Summary {get; init;}
    public decimal Rating {get; init;}
    public string Episode {get; init;}
    public string ParentalGuide {get; init;}

    // includeSummary is a method parameter
    public void PrettyPrint(bool includeSummary){
        if (includeSummary)
        {
            Console.WriteLine($"Adventure: {ShowName} {Episode} {Rating} {ShowLength} {Summary}");
        }
        else
        {
            Console.WriteLine($"Adventure: {ShowName} {Episode} {Rating} {ShowLength}");
        }
    }

    public bool IsGoodRating(){
        return Rating >= 3.5m;
    }
}

Reviewing the code we can see that while both the ComedyShow and AdventureShow classes are similar but they have different implementations of PrettyPrint and IsGoodRating. In addtion to different internals to the interface methods they each could have different private helper methods or even other public methods.

Lets assume our application permits users to enter tv show information and as part of that entry they can add the show as commedy or an adventure show. Let’s store that information in a list. Notice how InsertShow has a parameter TVShow but lower in the code when calling the method all objects that implement the TVShow interface can be added and worked on.

public static class Shows
{
    static List<TVShow> _tvShows = new List<TVShow>();

    public static void InsertShow(TVShow show)
    {
        _tvShows.Add(show);
    }

    public static void PrintShows()
    {
        foreach (var show in _tvShows)
        {
            show.PrettyPrint(includeSummary: true);
        }
    }
}

public static void Main()
{
    Shows.InsertShow(new ComedyShow() {
        ShowName = "Friends",
        ShowLength = 1380,
        Summary = "The friends get coffee.",
        Rating = 4.8m,
        Episode = "4x05",
        ParentalGuide = "PG13"
    });
    Shows.InsertShow(new AdventureShow() {
        ShowName = "Rick and morty",
        ShowLength = 760,
        Summary = "A quick 20 minute in and out adventure.",
        Rating = 3.8m,
        Episode = "3x14",
        ParentalGuide = "18A"
    });

    Shows.PrintShows();
}

The output is

Comedy: Friends 4x05 4.8 1380 The friends get coffee. Adventure: Rick and morty 3x14 3.8 760 A quick 20 minute in and out adventure.

For simplicity the example above is using a static Shows class. I almost always recommend against using static classes. I’ve shown their use in the above example as it is simple but in general I have found their use often coincides with global variables and long term they cause a maintenance quagmire. Static classes and variables have their place but try to avoid them.

Note: Read up about base classes and abstract bases classes as they are an alternative to using interfaces. Read about SOLID development.

Async/Await

Asynchronous programming . The core of async programming is the Task and Task objects, which model asynchronous operations. They are supported by the async and await keywords. The model is fairly simple in most cases: For I/O-bound code, you await an operation that returns a Task or Task inside of an async method. For CPU-bound code, you await an operation that is started on a background thread with the Task.Run method.

Async and await provides a way for more efficient use of threads. When a task is run it can be awaited later while doing more work while waiting.

Simple async/await example:

Private Async Function LoadPreviousSettings() As Task
	Threading.Thread.Sleep(5000)
End Function

Dim loadTask As Task = LoadPreviousSettings()

' Do some other crazy stuff

Await loadTask

private async Task LoadPreviousSettings()
{
	await Task.Delay(5000);
}

var loadTask = LoadPreviousSettings();

// Do some other crazy stuff

await loadTask

The async and await pattern makes asynchronous programming easiser and feels more like sequential development. Good places for async/await is I/O bound work such as when making network calls. Much of the time is spent waiting for a response and the thread could be doing other work while waiting. Network calls such as database connections, commands, updates, inserts, selects, deletes, and stored procedure and functions executions should be run with async and await pattern.

Another place async/await should be used is when making http calls. The example below demonstrates using async/await when using HttpClient to download a web site front page.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Threading.Tasks;
using System.Net.Http;

public static async Task Main()
{
    // normally disposable objects should be disposed.  
    // HttpClient is a special case and its norm is 
    // that it should not be exposed until the program terminates
	using var client = new HttpClient();
    // add all tasks to a list and later await them.
    var tasks = new List<Task<string>>();
     Stopwatch stopWatch = new Stopwatch();
    stopWatch.Start();
    for(int i=0; i<9; i++)
    {
        var instDownloader = new Downloader();
        tasks.Add(instDownloader.DownloadSiteAsync(client, "https://majorsilence.com"));
    }
    Console.WriteLine("majorsilence.com is being downloaded 10 times.  Waiting...");
    foreach(var t in tasks)
    {
        string html = await t;
        Console.WriteLine(html.Substring(0, 100));
    }
    stopWatch.Stop();
    TimeSpan ts = stopWatch.Elapsed;
    Console.WriteLine($"Code Downloaded in {ts.Milliseconds} Milliseconds");

    // sequential async calls
    Console.WriteLine("start sequential async calls to download majorsilence.com.  Waiting...");
    stopWatch.Start();
    for(int i=0; i<9; i++)
    {
        var instDownloader = new Downloader();
        string html = await instDownloader.DownloadSiteAsync(client, "https://majorsilence.com");
        Console.WriteLine(html.Substring(0, 100));
    }
    stopWatch.Stop();
    TimeSpan ts2 = stopWatch.Elapsed;
    Console.WriteLine($"Sequential Code Downloaded in {ts2.Milliseconds} Milliseconds");
}

public class Downloader{
    public async Task<string> DownloadSiteAsync(HttpClient httpClient,
        string url,
        System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken))
    {
        var request = new HttpRequestMessage()
            {
                Method = HttpMethod.Get,
                RequestUri = new Uri(url)
            };

        // proceed past user agent sniffing
        request.Headers.Add("User-Agent", "Mozilla/5.0 (X11; CrOS x86_64 14541.0.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/111.0.0.0 Safari/537.36");

        HttpResponseMessage response = await httpClient.SendAsync(request, cancellationToken).ConfigureAwait(false);

        response.EnsureSuccessStatusCode();
        return await response.Content.ReadAsStringAsync().ConfigureAwait(false); 
    }
}

Threads

In computer science, a thread of execution is the smallest sequence of programmed instructions that can be managed independently by a scheduler, which is typically a part of the operating system.

Dot net provides the Thread class.

Here is an example that starts a background tasks and checks every 500 millisecond if it is complete using the IsAlive property. If the background thread is still working it continues its work inside a while loop.

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

public class Program
{
    public static async Task Main()
    {
        var t = new Thread(ThreadMethod);
        t.Start();

        Console.WriteLine("Do other things while waiting for the background thread to finish");

        while(t.IsAlive){
            Console.WriteLine("Alive");
            await Task.Delay(500);
        }

        Console.WriteLine("job completed");
    }

    static void ThreadMethod(){
        Console.WriteLine("The code in this method is running in its own thread.");
        Console.WriteLine("Sleep the thread 5000 milliseconds to demonstrate the main thread keeps working.");
        Thread.Sleep(5000);
    }
}

This example starts a thread and does no work. The main thread stops work and waits for the background thread to complete using the Join method.

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

public class Program
{
    public static async Task Main()
    {
        var t = new Thread(ThreadMethod);
        t.Start();
        Console.WriteLine("Wait for the background thread to complete");
        t.Join();
        Console.WriteLine("job completed");
    }

    static void ThreadMethod(){
        Console.WriteLine("The code in this method is running in its own thread.");
        for(int i = 1; i< 6; i++){
            Console.WriteLine($"background loop count {i}");
            Thread.Sleep(500);
        }
    }
}

Locks

If more then one thread or task is updating a variable you should lock the variable as necessary.

The example below create multiple tasks that all update the same “count” variable. As you can see it locks the variable before updating it.

Dim tasks As New List(of Task)
Dim lockObject As New Object()

int count=0;

For i As Integer = 0 To 10
	tasks.Add(Task.Factory.StartNew(Function() 
		For j As Integer = 0 To 999
			SyncLock lockObject
				count = count + 1
			End SyncLock
		Next

	End Function))
Next

using System;
using System.Collections.Generic;
using System.Threading.Tasks;

public class Program
{
    public static async Task Main()
    {
        var tasks = new List<Task>();
		var lockObject = new object();

		int count = 0;
		for (int i = 0; i < 10; i++)
		{
			tasks.Add(Task.Factory.StartNew(() =>
			{
				for (int j = 0; j <= 999; j++)
				{
					lock (lockObject)
                    {
						count = count + 1;
					}        
				}
			}));
		}
		
		foreach(var t in tasks)
		{
			await t;
		}
		
		Console.WriteLine(count);
    }
}

Winforms

IOC

Repository Pattern

Use the repository pattern to seperate your business and data access layers. Makes it easy to test your business and data layer code seperatly.

There are different ways to do this. Here are a couple ways.

Use a base abstract class that is passed a connection

using System;
using System.Data;
using System.Data.SQLite;
using System.Threading.Tasks;

namespace MajorSilence.DataAccess
{
    public abstract class BaseRepo
    {
        private readonly string cnStr;

        protected BaseRepo(string cnStr)
        {
            this.cnStr = cnStr;
        }

        protected T WithConnection<T>(Func<IDbConnection, T> sqlTransaction)
        {
            using (var connection = new SQLiteConnection(cnStr))
            {
                connection.Open();
                return sqlTransaction(connection);
            }
        }

        protected void WithConnection(Action<IDbConnection> sqlTransaction)
        {
            using (var connection = new SQLiteConnection(cnStr))
            {
                connection.Open();
                sqlTransaction(connection);
            }
        }

        protected async Task<T> WithConnectionAsync<T>(Func<IDbConnection, Task<T>> sqlTransaction)
        {
            using (var connection = new SQLiteConnection(cnStr))
            {
                await connection.OpenAsync();
                return await sqlTransaction(connection);
            }
        }

        protected async Task WithConnectionAsync<T>(Func<IDbConnection, Task> sqlTransaction)
        {
            using (var connection = new SQLiteConnection(cnStr))
            {
                await connection.OpenAsync();
                await sqlTransaction(connection);
            }
        }
    }
}

And here is the repo class

using System;
using System.Linq;
using Dapper;

namespace MajorSilence.DataAccess
{
    public interface ITestRepo
    {
        string GetName();
        void InsertData(string name);
    }

    public class TestRepo : BaseRepo, ITestRepo
    {
        public TestRepo(string cnStr) : base(cnStr) { }

        public string GetName()
        {
            return this.WithConnection(cn =>
            {
                return cn.Query<string>("SELECT Name From TheTable LIMIT 1;").FirstOrDefault();
            });
        }

        public void InsertData(string name)
        {
            this.WithConnection(cn =>
            {
                cn.Execute("INSERT INTO TheTable (Name) VALUES (@Name);",
                    new { Name = name });
            });
        }
    }
}

No base abstract. Let individual repository classes do as they please

I generally prefer this way. It is simple.

using System.Data.SQLite;
using System.Linq;
using Dapper;

namespace MajorSilence.DataAccess
{

    public class TestRepoNobase : ITestRepo
    {
        readonly string cnStr;
        public TestRepoNobase(string cnStr)
        {
            this.cnStr = cnStr;
        }

        public string GetName()
        {
            using (var cn = new SQLiteConnection(cnStr))
            {
                return cn.Query<string>("SELECT Name From TheTable LIMIT 1;").FirstOrDefault();
            };
        }

        public void InsertData(string name)
        {
            using (var cn = new SQLiteConnection(cnStr))
            {
                cn.Execute("INSERT INTO TheTable (Name) VALUES (@Name);",
                    new { Name = name });
            };
        }
    }
}

Do something with the repository classes

A business class

using System;
namespace MajorSilence.BusinessStuff
{
    public class TestStuff
    {
        readonly DataAccess.ITestRepo repo;
        public TestStuff(DataAccess.ITestRepo repo)
        {
            this.repo = repo;
        }

        public void DoStuff()
        {
            repo.InsertData("The Name");
            string name = repo.GetName();

            // Do stuff with the name
        }
    }
}

Combine everything. Manualy initialize our two repository classes and initialize two copies of our TestStuff class. Our TestStuff never knows what or where the actual data layer is.

TestStuff is now easily tested with tools such as as moq.

using System;

namespace MajorSilence.TestStuff
{
    class Program
    {
        static void Main(string[] args)
        {

            // Our repository layer that will talk to the data source.
            // This could be inject with a dependency injection framework
            var repo = new MajorSilence.DataAccess.TestRepo("Data Source=:memory:;Version=3;New=True;");
            var repo2 = new MajorSilence.DataAccess.TestRepoNobase("Data Source=:memory:;Version=3;New=True;");


            // Our business class.  Takes an interface and does not care
            // what the actual data source is.
            var inst = new MajorSilence.BusinessStuff.TestStuff(repo);
            inst.DoStuff();

            var inst2 = new MajorSilence.BusinessStuff.TestStuff(repo2);
            inst2.DoStuff();
            
        }
    }
}

Events

Custom Event and Event Handlers

Use built in EventHandler

public class TheExample
{
    public event System.EventHandler DoSomething;

    public void TheTest(){
        // option 1 to raise event
        this.DoSomething?.Invoke(this, new System.EventArgs());

        // option 2 to raise event
        if (DoSomething != null)
        {
            DoSomething(this, new System.EventArgs());
        }
    }
}

Use custom delegate as event hander

public class TheExample
{
    public delegate void MyCustomEventHandler(object sender, System.EventArgs e);
    public event MyCustomEventHandler DoSomething;

    public void TheTest(){
        // option 1 to raise event
        this.DoSomething?.Invoke(this, new System.EventArgs());

        // option 2 to raise event
        if (DoSomething != null)
        {
            DoSomething(this, new System.EventArgs());
        }
    }
}

Susbscribe to the event

// subscribe using lamba expression

var x = new TheExample();

x.DoSomething += (s,e) => { 
    Console.WriteLine("hi, the event has been raised");
};  
x.TheTest

VB example of basic custom events

Public Class TheExample
    Public Delegate Sub MyCustomEventHandler(ByVal sender As Object, ByVal e As System.EventArgs)
    Public Shared Event MyCustomEventHandler As DoSomething

    Public Sub TheTest
        RaiseEvent DoSomething(Me, New EventArgs())
    End Sub
End Class

Subscribe to the event

dim x As New TheExample
AddHandler x.DoSomething, AddressOf
x.TheTest()

RemoveHandler x.DoSomething, AddressOf EventCallback

Sub EventCallback(ByVal sender As Object, ByVal e As System.EventArgs)
    Console.WriteLine("Hi, the event has been raised")
End sub

Create a custom event

Setup a new custom event class inherting from EventArgs and setup a new delegate.

public delegate void MyCustomEventHandler(object sender, MyCustomEvent e);

public class MyCustomEvent : System.EventArgs
{
        private string _msg;
        private float _value;

    public MyCustomEvent(string m)
    {
        _msg = m;
        _value = 0;
    }

    public MyCustomEvent(float v)
    {
        _msg = "";
        _value = v;
    }

    public string Message
    {
        get { return _msg; }
    }

    public float Value
    {
        get { return _value; }
    }
}

Use the custom event

public event MyCustomEventHandler DoSomething;

this.DoSomething?.Invoke(this, new MyCustomEvent(123.95f));

Nuget

Generally using nuget is very simple. Using Visual Studio right click your solution or project and select “Add Nuget Package”. Find your package and add it. It is auto added. Any time you now clone your project on a new computer the first time you build your project it will restore your nuget references.

Create a NuGet Package

write me

Add NuGet source

The following command will add a nuget source to your computer other than the default. This is good for self hosted nuget servers.

dotnet nuget add source "https://your.source.url/v3/index.json" -n [Feed Name] -u YourUserName -p YourPassword --store-password-in-clear-text

Check if NuGet Source already Exists

The following powershell script will check if a nuget source already exists on your computer.

dotnet nuget list source

Start fresh with just nuget.org

dotnet new nugetconfig

Testing

NUnit

NUnit is a fine testing framework for c#, vb and other .net based languages.

The nuget packages NUnit must be installed for base NUnit support in a test project and NunitXml.TestLogger should be installed for integration with the visual studio test tools and command line dotnet test and dotnet vstest.

dotnet add package NUnit --version 3.13.3
dotnet add package NunitXml.TestLogger --version 3.0.131

To demonstrate the the nunit testing framework we will work with a contrived example. The test class will test a modified threaded lock example from above.

Within the test class ComplexAdditionTests the code will confirm that the calculation works. This is helpful if a developer ever changes the CalculateWithLock method and breaks it. The test will fail and the develper will know that the change causes problems. The test will test the class ComplexAddition.

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using NUnit.Framework;

[TestFixture]
public class ComplexAdditionTests
{
    public async Task CalculationsCalculatesTest()
    {
        var complexAdds = new ComplexAddition();
        const int expectedResults =
        int actualResult = complexAdds.CalculateWithLock(10, 999);

        // 
        Assert.That(actualResults, Is.EqualTo(expectedResults));
    }
}

public class ComplexAddition
{
    public async Task<int> CalculateWithLock(int outerLimit=10, int innerLimit=999)
    {
        var tasks = new List<Task>();
		var lockObject = new object();

		int count = 0;
		for (int i = 0; i < outLimit; i++)
		{
			tasks.Add(Task.Factory.StartNew(() =>
			{
				for (int j = 0; j <= innerLimit; j++)
				{
					lock (lockObject)
                    {
						count = count + 1;
					}        
				}
			}));
		}
		
		foreach(var t in tasks)
		{
			await t;
		}
    }
}

The tests can be run from within visual studios test explorer or from the command line with either dotnet test or dotnet vstest.

dotnet test
dotnet vstest

Other test frameworks

Unit test frameworks:

xUnit
MSTest

Acceptance testing framework

FitNesse

BDD (Behavior-driven development) testing

SpecFlow

In Memory Work Queue

Task Queue

Thread Queue

Cyrstal Reports

Examples to use crystal reports from c#. Crystal reports for .net currently only support running on .net framework 4.8 and older. If reports need to be generated with .net core or .net 6 or newer see the CrystalCmd Server and Client section.

Make sure you have the crystal reports runtime installed. It can be downloaded from https://wiki.scn.sap.com/wiki/display/BOBJ/Crystal+Reports%2C+Developer+for+Visual+Studio+Downloads.

All examples below require references for CrystalDecisions.CrystalReports.Engine and CrystalDecisions.Shared to be added to your project.

Ensure the CrystalReports Version and PublicKey token match the installed version of Cyrstal Reports.

<Reference Include="CrystalDecisions.CrystalReports.Engine, Version=13.0.2000.0, 
Culture=neutral, PublicKeyToken=692fbea5521e1304, processorArchitecture=MSIL" />
<Reference Include="CrystalDecisions.Shared, Version=13.0.2000.0,
 Culture=neutral, PublicKeyToken=692fbea5521e1304, processorArchitecture=MSIL" />

Set data using DataTables

Example initializing a report and passing in a DataTable.

using CrystalDecisions.CrystalReports.Engine;
using CrystalDecisions.Shared;

// Pass a DataTable to a crystal report table
public static SetData(string crystalTemplateFilePath, 
    string pdfFilename, DataSet val)
{
    using (var rpt = new ReportDocument())
    {
        rpt.Load(crystalTemplateFilePath);
   
        rpt.Database.Tables["tableName"].SetDataSource(val);
    }
}

// Pass any generic IEnumerable data to a crystal report DataTable
public static SetData(string crystalTemplateFilePath, 
    IEnumerable<T> val)
{
    using (var rpt = new ReportDocument())
    {
        rpt.Load(crystalTemplateFilePath);
   
        var dt = ConvertGenericListToDatatable(val);
        rpt.Database.Tables[tableName].SetDataSource(val);
    }
}

// Found somewhere on the internet.  I know longer remember where.
public static DataTable ConvertGenericListToDatatable<T>(IEnumerable<T> dataLst)
{
    DataTable dt = new DataTable();

    foreach (var info in dataLst.FirstOrDefault().GetType().GetProperties())
    {
        dt.Columns.Add(info.Name, info.PropertyType);
    }

    foreach (var tp in dataLst)
    {
        DataRow row = dt.NewRow();
        foreach (var info in typeof(T).GetProperties())
        {
            if (info.Name == "Item") continue;
            row[info.Name] = info.GetValue(tp, null) == null ? DBNull.Value : info.GetValue(tp, null);
        }
        dt.Rows.Add(row);
    }
    dt.AcceptChanges();
    return dt;
}

Set report parameters

Set report parameters from code.

using CrystalDecisions.CrystalReports.Engine;
using CrystalDecisions.Shared;

public static void SetParameterValueName(string crystalTemplateFilePath, object val)
{
    using (var rpt = new ReportDocument())
    {
        rpt.Load(crystalTemplateFilePath);

        string name = "ParameterName";
        if (rpt.ParameterFields[name] != null)
        {
            this.MyReportDoc.SetParameterValue(name, val);
        }
    }
}

Move report objects

Example moving an object.

using CrystalDecisions.CrystalReports.Engine;
using CrystalDecisions.Shared;

public static MoveObject(string crystalTemplateFilePath)
{
    using (var rpt = new ReportDocument())
    {
        rpt.Load(crystalTemplateFilePath);
   
        rpt.ReportDefinition.ReportObjects["objectName"].Left = 15;
        rpt.ReportDefinition.ReportObjects["objectName"].Top = 15;
    }
}

Export to pdf or other file type

Load a report and export it to pdf. You can pass in data or set other properties before the export.

using CrystalDecisions.CrystalReports.Engine;
using CrystalDecisions.Shared;

public static ExportPdf(string crystalTemplateFilePath, 
    string pdfFilename)
{
    using (var rpt = new ReportDocument())
    {
        rpt.Load(crystalTemplateFilePath);
   
        var exp = ExportFormatType.PortableDocFormat;
        rpt.ExportToDisk(exp, pdfFilename);
    }
}

CrystalCmd Server and Client

crystalcmd is a:

Java and c# program to load json files into crystal reports and produce PDFs.

https://github.com/majorsilence/CrystalCmd

To host the cyrstalcmd .net server browse to https://github.com/majorsilence/CrystalCmd/tree/main/dotnet and build the Dockerfile.wine and Dockerfile.crystalcmd. If a java server is required use the prebuilt image at https://hub.docker.com/r/majorsilence/crystalcmd. The c# server is recommended.

With a crystalcmd server running crystal report templates and data can be sent to it to produce pdf files. The docker images can run on any system that supports docker such as mac, windows, and linux.

Add the package Majorsilence.CrystalCmd.Client to your project.

To call a crystalcmd server use the nuget package Majorsilence.CrystalCmd.Client.

dotnet add package Majorsilence.CrystalCmd.Client 

This example will call the server and return the pdf report as a stream.

DataTable dt = new DataTable();

// init reprt data
var reportData = new Majorsilence.CrystalCmd.Client.Data()
{
    DataTables = new Dictionary<string, string>(),
    MoveObjectPosition = new List<Majorsilence.CrystalCmd.Client.MoveObjects>(),
    Parameters = new Dictionary<string, object>(),
    SubReportDataTables = new List<Majorsilence.CrystalCmd.Client.SubReports>()
};

// add as many data tables as needed.  The client library will do the necessary conversions to json/csv.
reportData.AddData("report name goes here", "table name goes here", dt);

// export to pdf
var crystalReport = System.IO.File.ReadAllBytes("The rpt template file path goes here");
using (var instream = new MemoryStream(crystalReport))
using (var outstream = new MemoryStream())
{
    var rpt = new Majorsilence.CrystalCmd.Client.Report(serverUrl, username: "The server username goes here", password: "The server password goes here");
    using (var stream = await rpt.GenerateAsync(reportData, instream, _httpClient))
    {
        stream.CopyTo(outstream);
        return outstream.ToArray();
    }
}

Git

Github new repo example.

mkdir your_repo
cd your_repo
echo "" >> README.md
git init
git add README.md
git commit -m "first commit"
git branch -M main
git remote add origin git@github.com:YOUR_USERNAME/YOUR_REPO.git
git push -u origin main

Push an existing local repo to a new github repo.

git remote add origin git@github.com:YOUR_USERNAME/YOUR_REPO.git
git branch -M main
git push -u origin main

Git, show current branch.

git branch --show-current

Git, show remotes.

git branch --remotes

Git commit changes.

git commit -m "hello world"

Git pull/rebase from

git pull --rebase

Git pull from remote and branch.

git pull --rebase upstream main

Git Visual Studio

Git Rider

Tortoise Git

Github Desktop

Databases - Microsoft SQL

All sql scripts included in this section expect to be run in sql server management studio, azure data studio, or your preferred sql tool. If you need to install sql server skip to the SQL - Install section.

Adventure Works

While many of the sql examples shown will not use the adventure works sample database I suggest that it is restored and used to investigate sql server.

For a more detailed sample database download and restore Microsoft’s AdventureWorks database.

Before restoring the bak change the owner to mssql and move it to a folder that sql server has permissions to access.

sudo mkdir -p /var/opt/mssql/backup/
sudo chown mssql /var/opt/mssql/backup/
sudo chgrp mssql /var/opt/mssql/backup/
chown mssql AdventureWorksLT2019.bak 
chgrp mssql AdventureWorksLT2019.bak 
sudo mv AdventureWorksLT2019.bak  /var/opt/mssql/backup/

Find the logical names

USE [master];
GO
RESTORE FILELISTONLY 
FROM DISK = '/var/opt/mssql/backup/AdventureWorksLT2019.bak'

Restore the database.

USE [master];
GO
RESTORE DATABASE [AdventureWorks2019]
FROM DISK = '/var/opt/mssql/backup/AdventureWorksLT2019.bak'
WITH
    MOVE 'AdventureWorksLT2012_Data' TO '/var/opt/mssql/data/AdventureWorks2019.mdf',
    MOVE 'AdventureWorksLT2012_Log' TO '/var/opt/mssql/data/AdventureWorks2019_log.ldf',
    FILE = 1,
    NOUNLOAD,
    STATS = 5;
GO

Create a database

use master;
create database SqlPlayground;

Create a table

Create a table using a UNIQUEIDENTIFIER (sequential guid) column as the primary key.

use SqlPlayground;

create table [dbo].[TvShows]
(
    Id UNIQUEIDENTIFIER NOT NULL PRIMARY KEY DEFAULT NEWSEQUENTIALID(),
    ShowName nvarchar(50) not null,
    ShowLength int not null,
    Summary nvarchar(max) not null,
    Rating decimal(18,2) null,
    Episode nvarchar(200) not null,
    ParentalGuide nvarchar(5) null
)

As an alternative, create the table with a bigint identity column as the primary key.

create table [dbo].[TvShows]
(
    Id BIGINT NOT NULL IDENTITY PRIMARY KEY,
    ShowName nvarchar(50) not null,
    ShowLength int not null,
    Summary nvarchar(max) not null,
    Rating decimal(18,2) null,
    Episode nvarchar(200) not null,
    ParentalGuide nvarchar(5) null
)

Note: schemas, tables, and column names can be surrounded in square brackets []. This is for when special characters or reserved keywords are part of the name.

Alter a table

alter table TvShows
add FirstAiredUtc DateTime;

Review Clustered and nonclustered indexes described and CREATE INDEX.

create index index_tvshows_showname ON dbo.TvShows (ShowName);

SELECT

select * from TvShows;
select * from TvShows where Series = 'Dexter';
select Id, ShowName, ShowLength, Summary, FirstAiredUtc
from TvShows;

INSERT

Insert a new row into a table.

insert into TvShows (ShowName, ShowLength, Summary, Rating, Episode, ParentalGuide)
values ('Frasier', '30', 'Frasier goes home.', 4.56, '1e01', 'PG');

Insert a new row into a table and select back the new unique identifier of that row.

declare @InsertedRowIds table(InsertedId UNIQUEIDENTIFIER);

insert into TvShows (ShowName, ShowLength, Summary, Rating, Episode, ParentalGuide)
OUTPUT inserted.Id INTO  @InsertedRowIds(InsertedId)
values ('Frasier', '30', 'Frasier does it again.', 3.68, '2e01', 'PG');

select * FROM @InsertedRowIds; 

Insert a new row into a table that uses a bigint identity column and select back the new id of that row.

insert into TvShows (ShowName, ShowLength, Summary, Rating, Episode, ParentalGuide)
values ('Frasier', '30', 'Frasier does it again.', 3.68, '2e01', 'PG');

select SCOPE_IDENTITY();

UPDATE

When executing updates be sure to include a where clause to avoid updating every record in a table.

update TvShows set ParentalGuide = 'PG13' where ShowName='Friends'; 
update TvShows set ParentalGuide = 'PG' where ShowName = 'Frasier';
update TvShows set ParentalGuide = '18A' where ShowName = 'Dexter';
update TvShows set ParentalGuide = 'PG' where ShowName in ('Friends', 'Frasier'); 

DELETE

When executing deletes be sure to include a where clause to avoid deleting every record in a table.

delete from TvShows where ShowName = 'Dexter';

Foriegn Keys

JOIN

CTE

Stored Procedures

Stored Functions

Views

SQL - Install

SQL server windows install

Download sql server from Microsoft. The simple install method is to double click the setup.exe and use the user interface to complete the install.

If it is a non production environment, for development choose the developer edition.

If you wish to automate the install it can be script with options similar to the below example.

setup.exe /ACTION=INSTALL /IACCEPTSQLSERVERLICENSETERMS /FEATURES="SQL,Tools" /SECURITYMODE=SQL /SAPWD="PLACEHOLDER, PUT A GOOD PASSWORD HERE" /SQLSVCACCOUNT="NT AUTHORITY\Network Service" /SQLSVCSTARTUPTYPE=Automatic /TCPENABLED=1 /SQLSYSADMINACCOUNTS=".\Users" ".\Administrator" /SQLCOLLATION="SQL_Latin1_General_CP1_CI_AS"

Review the Install SQL Server on Windows from the command prompt page for up to date options and documentation.

SQL server linux install

See Quickstart: Install SQL Server and create a database on Ubuntu and for further details.

Run these commands to install sql server 2022 on a ubuntu server.

# Download the Microsoft repository GPG keys
wget -qO- https://packages.microsoft.com/keys/microsoft.asc | sudo tee /etc/apt/trusted.gpg.d/microsoft.asc
sudo add-apt-repository "$(wget -qO- https://packages.microsoft.com/config/ubuntu/$(lsb_release -rs)/mssql-server-2022.list)"
# Update the list of packages after we added packages.microsoft.com
sudo apt-get update
# Install PowerShell
sudo apt-get install mssql-server
sudo /opt/mssql/bin/mssql-conf setup

To enable the sql agent feature run this command:

sudo /opt/mssql/bin/mssql-conf set sqlagent.enabled true 
sudo systemctl restart mssql-server

If the command line tools are also required run these commands:

wget -qO- https://packages.microsoft.com/keys/microsoft.asc | sudo tee /etc/apt/trusted.gpg.d/microsoft.asc
wget -qO- https://packages.microsoft.com/config/ubuntu/$(lsb_release -rs)/prod.list | sudo tee /etc/apt/sources.list.d/msprod.list
sudo apt-get update
sudo apt-get install mssql-tools unixodbc-dev

echo 'export PATH="$PATH:/opt/mssql-tools/bin"' >> ~/.bash_profile

SQL server extra configuration after the install

Set some initial configuration options in sql management studio or azure data studio. Run the following sql.

sp_configure 'show advanced options', 1
reconfigure with override

sp_configure 'max server memory (MB)', -- 90% of OS MEM
reconfigure with override

SQL Management Studio
- sql options (database properties)
  - recovery model: full
    - If the data is non production or not important feel free to use the simple recovery mode.
  - Log and Data Growth: 10%
  - Compatiablity: latest version
  - Query Store - enable “Read write”
SQL Server Configuration Manager -> Protocols
- Set “Force Encryption” to “yes”

Reference - Admin

Use spBlitz (SQL First Responder Kit) to detect problems with sql server. Follow the instructions on the spBlitz site.

A few examples:

-- Realtime performance advice that should be run first when responding to an incident or case
exec sp_BlitzFirst

-- Overall Health Check
exec sp_Blitz

-- Find the Most Resource-Intensive Queries
exec sp_BlitzCache

-- Tune Your Indexes
exec sp_BlitzIndex

Use the Ola Hallengren SQL Server Maintenance Solutions for excellent pre-made community backed maintenance jobs.

azure data studio adminpack

azure data studio sql agent jobs

SQL Profiler

azure data studio launch profiler

azure data studio profiler 1

azure data studio profiler 2

SQL Query Store

SQL Watch

Databases - Redis

Session

Cache

Work and Message Queue

Database and DotNet

SqlConnection

SqlCommand

DataAdapters

Dapper

dotnet add package Dapper --version 2.0.123

using System.Data.SqlClient;
using Dapper;


await cn.OpenAsync();
var shows = await cn.QueryAsync<TvShow>("select * from TvShows");


public class TvShow
{
    public long Id {get; init;}
    public string ShowName {get; init;}
    public int ShowLength {get; init;}
    public string Summary {get; init;}
    public decimal Rating {get; init;}
    public string Episode {get; init;}
    public string ParentalGuide {get; init;}
}

Entity Framework

Fluentmigrator

Transactions and Isolation Levels

SQL Database Backup

Use SqlConnection and SqlCommand to create a bak copy only backup of a database.

using System.Data.SqlClient;

public async Task Backup(string connection, string saveFile,
    TimeSpan timout)
{
    string backupDir = System.IO.Path.GetDirectoryName(saveFile);
    if (System.IO.Directory.Exists(backupDir) == false)
    {
        System.IO.Directory.CreateDirectory(backupDir);
    }

    if (System.IO.File.Exists(saveFile)){
        System.IO.File.Delete(saveFile);
    }

    var csb = new SqlConnectionStringBuilder(connection);
    string database = csb.InitialCatalog;

    string sql = $"BACKUP DATABASE [{database}]";
    sql += $" TO DISK = '{saveFile}'";
    sql += " WITH FORMAT, COMPRESSION";
    sql += $" MEDIANAME = '{database}-Data',";
    sql += $" NAME = 'Full Backup of {database}',";
    sql += " COPY_ONLY;";

    using var cn = new SqlConnection(connection);
    using var cmd = new SqlCommand();

    cmd.CommandTimeout = timeout.TotalMinutes;
    await cn.OpenAsync();
    cmd.CommandText = sql;
    cmd.Connection = cn;

    await cmd.ExecuteNonQueryAsync();
}

ASP.Net Core

Dependency Injection

MVC

Minimal API

Blazor

Docker

nginx

Javascript and Typescript

fetch

Call service

Fetch post example

Call a service using post with fetch api. These examples uses helper functions that are defined in the Helper functions sub section below.

call fetch - form-urlencoded

Use a custom serialize helper method to transform an javascript object (json) to an form url encoded format.

Example:

?test_param=test value&another_param=another value

function PostFormUrlEncoded(msg) {
    var data = serialize({
        test_param: "test value",
        another_param: "another value"
    });

    return fetch(site + "/some/url", {
        method: 'POST',
        mode: 'cors',
        headers: {
            'Content-Type': 'application/x-www-form-urlencoded'
        },
        body: data
    });
}

PostFormUrlEncoded("My comment")
    .then(status_helper)
    .then(json_helper)
    .then(function(data) {
        console.log(data);
    })
    .catch(function(error) {
        console.log(error);
    });

call fetch - application/json

The content type application/json can use the builtin method JSON.stringify to send data.

function PostJson(msg) {
    var data = JSON.stringify({
        test_param: "test value",
        another_param: "another value"
    });

    return fetch(site + "/some/url", {
        method: 'POST',
        mode: 'cors',
        headers: {
            'Content-Type': 'application/json'
        },
        body: data
    });
}

PostJson("My comment")
    .then(status_helper)
    .then(json_helper)
    .then(function(data) {
        console.log(data);
    })
    .catch(function(error) {
        console.log(error);
    });

Helper functions

These helper functions implement some boiler plate code that will almost always be needed.

function status_helper(response) {
    if (response.status >= 200 && response.status < 300) {
        return Promise.resolve(response);
    }
    else {
        return Promise.reject(new Error(response.statusText));
    }
}

function json_helper(response) {
    return response.json();
}

function serialize(obj, prefix) {
    if (prefix === void 0) { prefix = null; }
    var str = [], p;
    for (p in obj) {
        if (obj.hasOwnProperty(p)) {
            var k = prefix ? prefix + "[" + p + "]" : p, v = obj[p];
            str.push((v !== null && typeof v === "object") ?
                serialize(v, k) :
                encodeURIComponent(k) + "=" + encodeURIComponent(v));
        }
    }
    return str.join("&");
}

async/await

Async and await support is built upon javascript promises. The following example is a slight modification on the PostJson example

Notice how the DownloadPage function is a GET and does not have a mode, headers, or body. A body must not be set on a GET but the other properties are setable. DownloadPage returns the response.text().

In contrast the PostJson function is a POST and sets the mode to cors, headers, and a body. PostJson returns the response.json().

async function DownloadPage(url) {
    const response = await fetch(url, {
        method: 'GET'
    });

    if (response.status < 200 && response.status > 299) {
        throw new Error(response.status);
    }

    return response.text();
}

async function PostJson(url, msg) {
    var data = JSON.stringify({
        test_param: "test value",
        another_param: "another value"
    });

    const response = await fetch(url, {
        method: 'POST',
        mode: 'cors',
        headers: {
            'Content-Type': 'application/json'
        },
        body: data
    });

    if (response.status < 200 && response.status > 299) {
        throw new Error(response.status);
    }

    return response.json();
}

PostJson("https://majorsilence.com/non/existing/post/page", "My comment")
    .then(function(data) {
        console.log(data);
    })
    .catch(function(error) {
        console.log(error);
    });

DownloadPage("https://majorsilence.com")
    .then(function(data) {
        console.log(data);
    })
    .catch(function(error) {
        console.log(error);
    });

jQuery

Kendo UI

Microsoft Maui

Monitoring

Prometheus

Grafana

Kubernetes

# use multiple kubeconfig files at the same time and view merged config
KUBECONFIG=~/.kube/config:~/.kube/kubconfig2
kubectl config view
kubectl config get-contexts
kubectl config current-context
kubectl get nodes
kubectl get namespaces
kubectl -n theNamespace get all
kubectl -n theNamespace get pods
kubectl -n theNamespace get deployments
kubectl -n theNamespace get service
kubectl -n theNamespace get ingress
kubectl -n theNamespace describe deployment theDeployment

# create a new pod yaml file.  Edit the pod.yaml file to your needs.
kubectl run nginx --image=nginx --dry-run=client -o yaml > pod.yaml
kubectl create -f pod.yaml

C# and VB Basics

Variables

Integers

Strings

StringBuilder

Decimals

Booleans

Chars

DateTime

Doubles

Objects

Objects

Methods

Interfaces

Async/Await

Threads

Locks

Winforms

IOC

Repository Pattern

Use a base abstract class that is passed a connection

No base abstract. Let individual repository classes do as they please

Do something with the repository classes

Events

Use built in EventHandler

Use custom delegate as event hander

Susbscribe to the event

VB example of basic custom events

Create a custom event

Use the custom event

Nuget

Create a NuGet Package

Add NuGet source

Check if NuGet Source already Exists

Start fresh with just nuget.org

Testing

NUnit

Other test frameworks

In Memory Work Queue

Task Queue

Thread Queue

Cyrstal Reports

Set data using DataTables

Set report parameters

Move report objects

Export to pdf or other file type

CrystalCmd Server and Client

Git

Git Visual Studio

Git Rider

Tortoise Git

Github Desktop

Databases - Microsoft SQL

Adventure Works

Create a database

Create a table

Alter a table

SELECT

INSERT

UPDATE

DELETE

Foriegn Keys

JOIN

CTE

Stored Procedures

Stored Functions

Views

SQL - Install

SQL server windows install

SQL server linux install

SQL server extra configuration after the install

Reference - Admin

SQL Profiler

SQL Query Store

SQL Watch

Databases - Redis

Session

Cache

Publish and Subscribe

Work and Message Queue