You go to the TextBox Properties/Events Icon/Focus/Enter and you give
the event a name like Textbox1_GotFocus or prefix it with whatever the
name of the textbox is. In the event, you call the TextboxHighlight
routine, giving it the Textbox control.

You can de-select the highlight by setting SelectionLength = 0

        private void TextBox1_GotFocus(object sender, EventArgs e)
        {
            TextboxHighlight(textBox1);

        }

        private void TextboxHighlight(TextBox cntrl)
        {
            int ilen = cntrl.Text.Length;
            cntrl.SelectionLength = ilen;
        }

Then all you have to do is Textbox1.Focus, and if there is text in the
Textbox, it's going to be highlighted.

"AVL" <AVL@discussions.microsoft.com> schrieb:

In addition to the other reply, note that 'Focus' will fail if the form is
not yet visible.  You may want to use 'Select' instead.