Get ClientID of a parameter on an ASP site

Question

I have a parameter for a method, that should be a string and I can't come up with how to <% *.ClientID %> to the thing as a variable like that. Since its a variable i can't wrap it in quotes since it will be taken literally and when I use the parameter like a variable (as you're supposed to) i get an ASP error saying it doesn't exist in the context (reading it literally).

Any Clues?

thanks guys

Code Sample

function next(currentControl, maxLength, nextControl) { 
   if (document.getElementById( currentControl<%=.ClientID %>).value.length >= maxLength) {
         document.getElementById( nextControl<%=.ClientID %>).focus(); 
   } 
   return false; 
} 

Call Sample

wValCode.Attributes.Add("onkeyup","next('wValCode','3','wValThree')");

I know probably a primitive way of adding the attribute, but its how it was explained to me. I picked up ASP on the fly so don't be too hard on me ;)

Static HTML

<input name="ctl00$ContentPlaceHolder2$wValThree" type="text" id="ctl00_ContentPlaceHolder2_wValThree" style="width:33px;">

That is the only related reference I can find in the static html. Would it have been added in one of ASPs convoluted js files?

Answer 1

Try moving the dot outside the ASP.NET tag:

currentControl.<%= ClientID %>

Answer 2

Given you're binding the key events from code behind, you can just reference the client IDs at the time that you're doing the binding:

wValCode.Attributes.Add("onkeyup","next('" + wValCode.ClientID + "', '3', '" + wValThree.ClientID + "')");

Then, you already have the client IDs passed as parameters to the javascript function

function next(currentControl, maxLength, nextControl) { 
   if (document.getElementById(currentControl).value.length >= maxLength) {
         document.getElementById(nextControl).focus(); 
   } 
   return false; 
}

An even better option is to pass a reference to the calling object as the first parameter, using the this keyword:

//code behind
wValCode.Attributes.Add("onkeyup","next(this, '3', '" + wValThree.ClientID + "')");

//javascript function
function next(currentControl, maxLength, nextControl) { 
   if (currentControl.value.length >= maxLength) {
         document.getElementById(nextControl).focus(); 
   } 
   return false; 
}