UpdatePanel does not work with Code Blocks

Question

Hi,

I have a reference to a control (rcbModels) using a codeblock like this

  function pageLoad() {

      models = $find("<%= rcbModels.ClientID %>");
  }

I added an UpdatePanel to this page but I always get the following error: "The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>)."

I have tried changing the codeblock to:

      function pageLoad() {

      models = $find("<%# rcbModels.ClientID %>");
  }

And DataBinding on the Pre_RenderComplete event without success.

What's the best way to solve this issue ?

Answer 1

Looking at http://www.telerik.com/community/forums/aspnet/editor/the-controls-collection-cannot-be-modified-because-the-control-contains-code-blocks-i-e-lt-gt.aspx

it seems that this could be caused by the runat="server" in the head tag. moving the javascript code into the body but still outside the update panel may remedy this.

Answer 2

For simple cases (trivial page, container chain to rcbModels never changing, code quality not a concern), hardcoding rcbModels.ClientId into the script block saves time and gets the job done.

function pageLoad()
{
    models = $find("panelX_containerY_rcbModels");
}

In other cases, generate a page-wide, client-side dictionary of controls ids mapping to client ids.

protected void Page_PreRender(object sender, EventArgs e)
{
    ScriptManager.RegisterClientScriptBlock(this, typeof(YourPageClass),
        "__BehaviorIds", String.Format(CultureInfo.InvariantCulture, @"
            var __BehaviorIds = {{
                rcbModels: '{0}',
                anotherControl: '{1}',
                yetAnotherControl: '{2}'
            }};",
        rcbModels.ClientID,
        anotherControl.ClientID,
        yetAnotherControl.ClientID), true);
}

Then you can access the behavior ids by name on the client side.

function pageLoad()
{
    models = $find(__BehaviorIds.rcbModels);
    anotherControl = $find(__BehaviorIds.anotherControl);
    yetAnotherControl = $find(__BehaviorIds.yetAnotherControl);
}

Answer 3

Thanks for your response. What I ended up doing was changing the "=" for a "#" and adding a DataBind() clause in the code behind and that solved it.

function pageLoad() {   

  models = $find("<%# rcbModels.ClientID %>");   
 }   




protected void Page_Load(object sender, EventArgs e)   
{      
     Page.Header.DataBind();       
}