Question

I have Main.Master, an inner master page Inner.Master, and abc.aspx. In Inner.Master I have a dropdownlist ddlChildren which I populate on Inner.Master page load.

I would like to, on loading page abc.aspx, I get access to ddlChildren from its master page, Inner.Master:

int x = Int32.Parse(((DropDownList)this.Parent.FindControl("ddlChildren")).SelectedValue);

I am doing this on page load of abc.aspx. The problem is this control is not found. I think this happens becuase the control is not even loaded yet in Inner.Master, because when I do:

this.Parent.Controls.Count

at debugging, I only have 1 control for Inner.Master, which its Main.Master.

I then tried to call ddlChildren onPreRender, but the same Happens.

According to http://msdn.microsoft.com/en-us/library/ms178472.aspx, controls are loaded at pre render, but the on pre render of inner master is called AFTER abc.aspx. So can I do this at another page stage?

Or am I completely off track?

Answer 1

Visual breakdown of the lifecycle, including master pages.

OK, I think there is more going on here.

First of all FindControl isn’t recursive, unless what you are looking for is a direct child of the object in question, you won’t find it.

You’ll need a function something like this (not tested, but I’ve written something like it before):

private WebControl FindControlRecursive(WebControl parentControl, string controlId)
{
    if( !parentControl.Controls.Any())
        return null;

    var foundControl = parentControl.FindControl(controlId);

    if(foundControl == null)
    {
        foreach(child in parentControl.Controls)
        {
            var foundChild = FindControlRecursive(child, controlId);

            if(foundChild != null)
                return foundChild;    
        }
    }

    return foundControl;
}

Second, you’re assuming Parent of your page is the master page. This may not be true. Try Page.MasterPage detailed here.

So, to conclude, try this:

var dropDown = (DropDownList)FindControlRecursive(Page.MasterPage, "ddlChildren");

One more thing. It’s usually good to consider that if you find yourself accessing controls that exist in a level above your current Page scope, you may want to rethink your design.