how to permit only letters in a textbox in windows forms application?

Question

to permit letters from A to Z what is the source code in C#?

Answer 1

on leave event check string and show error or force focus

Answer 2

You can either validate the input after the user has "finished", or capture the KeyPress event and supress the event if the key isn't a letter.

Answer 3

If you go down the route of validation, use the TextChanged event of the textbox to check whether the .text contains any non-A-Z characters. If so, use the .SetError method of an ErrorProvider to indicate to the user that there is a problem with what they have input.

    if (!Regex.IsMatch(textbox.Text, @"[a-zA-Z]"))
{
  yourErrorProvider.setError(textbox, "Only A-Z accepted.");
}

Answer 4

in your constructor or via designer:

textBox.KeyPress += new KeyPressEventHandler(textBox_KeyPress);

Then the event handler:

private void textBox_KeyPress(object sender, KeyPressEventArgs e)
{
    if (e.KeyChar < 65 || e.KeyChar > 122)
    {
        e.Handled = true;
    }
}