Add Html/javascript Event In ASP.NET(C#)

 <Script language="javascript">
function CheckToInteger(events){
    events = (events) ? events : window.event;
    var charCode = (events.which) ? events.which : events.keyCode;
    if (charCode < 48 || charCode > 57) {
        status = "This field accepts integer only.";      
        return false;
    }
    status = "";   
    return true;
}
</script>

add below cord in ".cs" file:

this.tbSysPrm.Attributes.Add("onkeypress", "return CheckToInteger()");