C#如何把写字板文件、TXT文件读入RichTextBox

System.Windows.Forms.DialogResult dr;
dr = openfiledialog1.ShowDialog();
if (dr == System.Windows.Forms.DialogResult.OK)
{
richTextBox1.LoadFile(openfiledialog1.FileName, System.Windows.Forms.RichTextBoxStreamType.PlainText);
}

用这个，已经调试成功，使用openfiledialog1打开txt文件

System.Windows.Forms.DialogResult dr;
dr = openfiledialog1.ShowDialog();
if (dr == System.Windows.Forms.DialogResult.OK)
{
richTextBox1.LoadFile(openfiledialog1.FileName, System.Windows.Forms.RichTextBoxStreamType.PlainText);
}