Disable and Restrict Copy Cut and Paste from on a textbox

You will need two javascript functions for this:

function noCopyMouse(e){ 
  var isRight = (e.button) ? (e.button == 2) : (e.which == 3); 
  if(isRight){ 
    alert('You are prompted to type this twice for a reason!');
  return false;
  } 
  return true; 
} 

function noCopyKey(e) { 
var forbiddenKeys = new Array('c','x','v');
var keyCode = (e.keyCode) ? e.keyCode : e.which; 
var isCtrl;

  if(window.event) 
  isCtrl = e.ctrlKey 
  else 
  isCtrl = (window.Event) ? ((e.modifiers & Event.CTRL_MASK)

  == Event.CTRL_MASK):false; 

  if(isCtrl){

    for(i = 0; i < forbiddenKeys.length; i++) { 
     if(forbiddenKeys[i] == String.fromCharCode(keyCode).toLowerCase()){
       alert('You are prompted to type this twice for a reason!');
       return false; 
     } 
    } 
  } 
  return true; 
}

And a wee bit of code-behind to handle the two events for the textbox(es):

Textbox1.Attributes.Add("onmousedown", "return noCopyMouse(event);");
Textbox1.Attributes.Add("onkeydown", "return   noCopyKey(event);");

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Realize that the user can still use Edit|Copy and Edit|Paste in their browser menu.  There's nothing you can do to prevent that, unfortunately.
Hope this helps!  Don't forget to mark the most helpful post(s) as Answer for the sake of future readers.  Thanks!