如何在ext.net文本字段中禁用复制？

 <ext:TextField runat="server" ID="txtTruck" FieldStyle="text-transform: uppercase;" regex="^[A-Za-z0-9-.]+$" MarginSpec="4 5 5 9" LabelAlign="left" Disabled="true">
          <Listeners>
              <AfterRender Handler="this.el.dom.setAttribute('onPaste', 'return false');" />
          </Listeners>

 </ext:TextField>
 <ext:TextField runat="server" ID="txtTruck" Fi