Question

I have an ASP.NET user control that contains a text box control and a button control. This user control will be added to my web-page many times. I need to have a piece of JavaScript that will run whenever the text box changes, and disable the button if the value of the text box is invalid. My question is this: how do I put JavaScript on the textbox that can reference only the button that is in the same user control? Remember, there are many ASP.NET user controls, each with a button and a text box, and I only want the invalid value in a text box to affect the one associated button. Thanks!

Answer 1

You can use ClientId property of controls (it’s uniquely identifies control on the client side) and make something like that:

<asp:TextBox runat='server' ID='myTextBox' /> <asp:Button runat='server' ID='myButton' Text='click' />  <script language='javascript' type='text/javascript'>     document.getElementById('<%=myTextBox.ClientID %>').onclick = function() {         document.getElementById('<%=myButton.ClientID %>').disabled = 'disabled';     } </script> 

Also refer to this document: Client Script in ASP.NET Web Pages, section Referencing Server Controls in Client Script