Eu escrevi o código a seguir para acrescentar os dados com os dados existentes, como é, mas o meu código substitui este

o que devo fazer as alterações no código de anexar dados.

protected void Page_Load(object sender, EventArgs e)
{
    fname = Request.Form["Text1"];
    lname = Request.Form["Text2"];
    ph = Request.Form["Text3"];
    Empcode = Request.Form["Text4"];

    string filePath = @"E:Employee.txt";
    if (File.Exists(filePath))
    {
        //StreamWriter SW;
        //SW = File.CreateText(filePath);
        //SW.Write(text);
        //SW.Close();
        FileStream aFile = new FileStream(filePath, FileMode.Create, FileAccess.Write);
        StreamWriter sw = new StreamWriter(aFile);
        sw.WriteLine(Empcode);
        sw.WriteLine(fname);
        sw.WriteLine(lname);
        sw.WriteLine(ph);
        sw.WriteLine("**********************************************************************");

        sw.Close();
        aFile.Close();
    }
    else
    {
        //sw.Write(text);
        //sw.Flush();
        //sw.Close();
        //StreamWriter SW;
        //SW = File.AppendText(filePath);
        //SW.WriteLine(text);
        //SW.Close();

        FileStream aFile = new FileStream(filePath, FileMode.Append, FileAccess.Write);
        StreamWriter sw = new StreamWriter(aFile);

        sw.WriteLine(Empcode);
        sw.WriteLine(fname);
        sw.WriteLine(lname);
        sw.WriteLine(ph);
        sw.WriteLine("**********************************************************************");

        sw.Close();
        aFile.Close();
        //System.IO.File.WriteAllText(filePath, text);
    }
    Response.Write("Employee Add Successfully.........");
}