For a charity project I took the time to employ a barebones inheritance approach to web page design. A basewebpage loads a basepagetemplate usercontrol which loads three page controls, one of which is the bodycontrol which itself loads one or more controls. This allows me to isolate code to a single control, the only “new“ coding required for any given application. This works great until I try to create an object reference between two controls loaded from the bodycontrol (which is loaded from the basepagetemplate control.) As in
protected SiteNews sitenews;
Label lblNews = (Label) sitenews.FindControl("lblMenu");
lblNews.Text = "hello from Profile Control!";
...and many variants on the above code.
I can't seem to get past the “Object Reference not set to an instance of an object“ runtime error.
This is not something I have to do, just something I wanted to do to understand how to do it. After several latenight hours I decided to put this on hold. I GUESS it can be done, but since this quest was primarily an academic one, if it CAN be done I'll figure it out later.
So on the latenight R&D shelf for now: understanding how to talk between two controls deep in the loaded control heriarchy.
[UPDATE]
A big thanks to the guys who commented on this. I thought about each comment, but what struck a chord was Scott Allen's statement that the control ID might be "munged" (that would be a soft "g"). Yes, when I had previously checked out the HTML source, I saw stuff like
<span id="_ctl0__ctl2_uc_sitenews_lblNews" class="mredstart"></span>
and knew I was seeing something related to the “object reference not set...” error. So I grabbed the label's UNIQUEID property with lblNews.Text = lblNews.UniqueID.ToString(). It was something like
_ctl0:_ctl2:uc_sitenews:lblNews
So I used the UniqueID with a Page.FindControl method, as in
Label.lblNews = (Label) Page.FindControl(”_ctl0:_ctl2:uc_sitenews:lblNews”);
which worked.
As I said in the subject [update], this is ugly and it may in fact be wrong, but hey, it works.
In review, WHAT works? I can now seem to reference any object in any control from any other control in a “multi-layered” inherited design with dynamically loaded control. Sounds like a sweeping pronunciation, doesn't it?