how to find out first character index in my textbox

Question

i have a textbox, i need to enter only alphabet in the starting of textbox.. no integers, no special characters.... what should i do?

Answer 1

You can use the TextBox.Validated event and match the content with RegEx.
Take a look here.

Answer 2

Using javascripts match() method and the following RegularExpression should do the trick

^[a-zA-Z].*

Here is a short example of how to implement the match method with the regex above

<script type="text/javascript">
  function validate()
  {
      var textBoxToValidate = document.getElementById('Text1');
      if(textBoxToValidate.value.match('^[a-zA-Z].*'))
      {
          alert('Is valid');
      }  
      else
      {
          alert('Is invalid');
      }
  }
</script>

<input id="Text1" type="text" />
<input id="Button1" type="button" value="button" onclick="validate()" />

Answer 3

If you are doing this client side, you could use an asp:RegularExpressionValidator control in the following manner.

<asp:TextBox ID="inputBox" runat="server" /><br />
<asp:RegularExpressionValidator 
    runat="server" 
    ControlToValidate="inputBox" 
    ValidationExpression="^[a-zA-Z].*" 
    ErrorMessage="Input must start with a letter" />

Server side, you could simply check the first character by using char.IsLetter.

bool isValid = char.IsLetter(inputBox.Text[0]);

Answer 4

In the script function fnalpha() { if(event.keycode>=65 && event.keycode<=90 || event.keycode>=97&&event.keycode<=122) event.retrunValue=true; else event.returnValue=false; }

in the source of textbox, call this method onkeypress="return fnalpha()";

i tried like this... worked properly...