Load File From The Open Dialog box As Text Format Or As RTF Format...

string filename=null;

//On The Load Button's Click Event...

private void btnLoad_Click(System.Object sender, System.EventArgs e)

{

       if (OpenFileDialog1.ShowDialog == DialogResult.OK)

{

              //Store Filename Into The Variable...

              filename = OpenFileDialog1.FileName;

              //Load Selected Text Format Or RTf Format File in RichTextBox...

RichTextBox1.LoadFile(filename);

}

}