C# TextBox 컨트롤+A Ctrl+A 동작하게 하기..

protected override bool ProcessDialogKey(Keys keyData)
{
	switch (keyData)
	{
		case Keys.A | Keys.Control:
			if (this.ActiveControl is TextBox)
			{
				TextBox txt = (TextBox)this.ActiveControl;
				txt.SelectionStart = 0;
				txt.SelectionLength = txt.Text.Length;
				return true;
			}
			break;
	}
	return base.ProcessDialogKey(keyData);
}