How to use KeyPress event for ASP.Net TextBox

Yes but it will be only client side i.e. JavaScript

 <asp:TextBox ID="TextBox1" runat="server" onkeypress = "GetKeyCode(event)" />

<script type = "text/javascript">
    function GetKeyCode(evt)
    {
        var keyCode;
        if(evt.keyCode > 0)
        {
            keyCode = evt.keyCode;
        }
        else if(typeof(evt.charCode) != "undefined")
        {
            keyCode = evt.charCode;
        }
        alert("You pressed : " + keyCode);
    }
</script>