1st and very simple way:
Using RegularExpressionValidator <asp:TextBox runat="server" Id="txt_policy_code" />
<asp:RegularExpressionValidator runat="server" id="rex_policy_code" ControlToValidate="txt_policy_code" ValidationExpression="^[a-zA-Z0-9]$" ErrorMessage="Only Alpha-Numeric Allowed" />
2nd way:
Using Javascript: function checkAlphaNumeric(e)
{
if ((e.keyCode >= 48 && e.keyCode <= 57) ||
(e.keyCode >= 65 && e.keyCode <= 90) ||
(e.keyCode >= 97 && e.keyCode <= 122))
{
return true;
}
return false;
}
<asp:Textbox Id="txt_policy_code" runat="server" onKeyPress="return checkAlphaNumeric();"></asp:Textbox>