Allow only character in text box, not number

It's a web app, according to your tags, so you need to write some JavaScript validation code. 'onchange' is the event in the DOM that corresponds to TextChanged. You should also handle 'onkeypress' and reject numbers, because modifying the text in onchange causes the caret position to be reset and that's annoying if it happens every time you enter an invalid character.

You can also do this using simple javascript:

function AllowAlphabet(e)
{
  isIE = document.all ? 1 : 0
  keyEntry = !isIE ? e.which : event.keyCode;
  if (((keyEntry >= '65') && (keyEntry <= '90')) || ((keyEntry >= '97') && (keyEntry <= '122')) || (keyEntry == '46') || (keyEntry == '32') || keyEntry == '45')
     return true;
  else
{
    alert('Please Enter Only Character values.');
    return false;
      }
}

<asp:textbox id="TextBox1" runat="server" maxlength="1" onkeypress="return AllowAlphabet(event)" xmlns:asp="#unknown"></asp:textbox>

There are a couple of ways, but the most reliable is to handle the TextChanged Event and screen the entire text. This prevents pasting digits as well, which the KeyPress Event doesn't.

private void myTextBox_TextChanged(object sender, EventArgs e)
    {
    Regex r = new Regex(@"\d");
    if (r.IsMatch(myTextBox.Text))
        {
        int i = myTextBox.SelectionStart;
        myTextBox.Text = r.Replace(myTextBox.Text, "");
        myTextBox.SelectionStart = i;
        }
    }

(the SelectionStart stuff is to preserve the caret position)

Maybe this can help

www.codeproject.com/Answers/55378/validate-a-text-box-only-enter-numeric-value-in-ja.aspx#answer1[^]

hello friend try this code

ValidationExpression="^[a-zA-Z''-'\s]{1,40}$"