Any appropriate syntax for my.computer.filesystem.opentextfilewriter in C# ?

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C#

VB

I have the following function in vb.net that I want to convert it in C# in order to create a set up file for trial and licenced version of application.
I used several converters because I was facing converting issues.

<pre> 
<pre> Public Sub ReWriteToFile(ByVal Name As String, ByVal Value As String)
        Dim File As IO.StreamWriter


        Dim fileContents = IO.File.ReadAllText("C:\BackgammonTxt\AppDataFile.txt")
        File =
            My.Computer.FileSystem.OpenTextFileWriter("C:\BackgammonTxt\AppDataFile.txt", True)

        'Dim attributes As FileAttributes = IO.File.GetAttributes("C:\BackgammonTxt\AppDataFile.txt")

        'If Not (attributes And FileAttributes.Hidden) = FileAttributes.Hidden Then
        '    IO.File.SetAttributes("C:\BackgammonTxt\AppDataFile.txt",
        '                       IO.File.GetAttributes("C:\BackgammonTxt\AppDataFile.txt") Or FileAttributes.Hidden)
        '    'MsgBox("The file is now hidden ")
        'End If
        IO.File.SetAttributes("C:\BackgammonTxt", IO.FileAttributes.Normal)
        IO.File.SetAttributes("C:\BackgammonTxt\AppDataFile.txt", IO.FileAttributes.Normal)

        File.Close()

        Dim FileStr As String = "C:\BackgammonTxt\AppDataFile.txt"
        Dim newline As String = Name & Value.ToString

        If System.IO.File.Exists(FileStr) Then
            Dim lines() As String = IO.File.ReadAllLines(FileStr)
            For i As Integer = 0 To lines.Length - 1
                If lines(i).Contains(Name) Then
                    lines(i) = newline
                End If
            Next
            IO.File.WriteAllLines(FileStr, lines) 'assuming you want to write the file
        End If

        File.Close()
    End Sub

What I have tried:

<pre lang="C#">
<pre> public void ReWriteToFile(string Name, string Value)
        {
            System.IO.StreamWriter File;


            var fileContents = System.IO.File.ReadAllText(@"C:\BackgammonTxt\AppDataFile.txt");
            File = My.Computer.FileSystem.OpenTextFileWriter(@"C:\BackgammonTxt\AppDataFile.txt", true);
            
            System.IO.File.SetAttributes(@"C:\BackgammonTxt", System.IO.FileAttributes.Normal);
            System.IO.File.SetAttributes(@"C:\BackgammonTxt\AppDataFile.txt", System.IO.FileAttributes.Normal);

            File.Close();

            string FileStr = @"C:\BackgammonTxt\AppDataFile.txt";
            string newline = Name + Value.ToString();

            if (System.IO.File.Exists(FileStr))
            {
                string[] lines = System.IO.File.ReadAllLines(FileStr);
                for (int i = 0; i <= lines.Length - 1; i++)
                {
                    if (lines[i].Contains(Name))
                        lines[i] = newline;
                }
                System.IO.File.WriteAllLines(FileStr, lines); // assuming you want to write the file
            }

            File.Close();
        }

I am getting error in

File = My.Computer.FileSystem.OpenTextFileWriter(@"C:\BackgammonTxt\AppDataFile.txt", true);

I want to be able to append data on the file and I don't understand how to change this line of source code to make it work.
I found something like the following but I am not pretty sure if it is right, because we don't have any parameter, as append boolean flag. The syntax is different. I would like to have the right one, with an explanation please. Thank you so much in advanced.

File = new System.IO.StreamWriter(@"c:\test2\test.txt");