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();
    }
}