JQuery:preventDefault() method will do.

e.preventDefault() is the key method, to disable the default operations to proceed further. We first stop the event from further bubbling up to other parent controls and put any custom logic.

@"e" is a event.


Example:
$('#<%=textbox.ClientID%>').bind('cut copy paste',
function (e) {
e.preventDefault();
alert("Cut / Copy / Paste are not allowed.");

});