Referencing a parent control from a child?

30 Jul 2006 10:09 PM

Steve Hershoff

I have two UserControls I'd like to have talk to each other. One of them is
contained within the other, in a parent/child relationship. The child
control is loaded dynamically (it's declared as a WebControls.Placeholder)
in the parent through a call to LoadControl().

I'm using events to communicate between them. The parent will fire an
event, and if the child is listening it will do something. That's the idea
at least.

In practice I'm having trouble getting the parent's reference while in the
child. My code looks like this:

public abstract class MyChildControl : System.Web.UI.UserControl {
.....
protected MyParentControl parent;
.....
parent = (MyParentControl) this.Parent; //big blowup here
.....
}

I'm getting an invalid cast error when I call the last line. Obviously I'm
not clear on how to go about getting a reference to the parent from within
the child. Could someone show me the proper way of doing this? Thanks very
much.

30 Jul 2006 10:45 PM

Jens Hofmann

Steve Hershoff schrieb:
Show quoteHide quote

> I have two UserControls I'd like to have talk to each other. One of them is
> contained within the other, in a parent/child relationship. The child
> control is loaded dynamically (it's declared as a WebControls.Placeholder)
> in the parent through a call to LoadControl().
>
> I'm using events to communicate between them. The parent will fire an
> event, and if the child is listening it will do something. That's the idea
> at least.
>
>
> In practice I'm having trouble getting the parent's reference while in the
> child. My code looks like this:
>
> public abstract class MyChildControl : System.Web.UI.UserControl {
> .....
> protected MyParentControl parent;
> .....
> parent = (MyParentControl) this.Parent; //big blowup here
> .....
> }
>
> I'm getting an invalid cast error when I call the last line. Obviously I'm
> not clear on how to go about getting a reference to the parent from within
> the child. Could someone show me the proper way of doing this? Thanks very
> much.
>
>

Hello,

first I would set a breakpoint to this line and check what type of
object this.Parent is. Maybe it's a Panel .. or some other Container...

....
parent = (MyParentControl) this.Parent
....

30 Jul 2006 11:57 PM

Peter Bromberg [C# MVP]

If it doesn't absolutely "have to be" abstract, that's another area that
could cause this problem.
Peter

--
Co-founder, Eggheadcafe.com developer portal:
http://www.eggheadcafe.com
UnBlog:
http://petesbloggerama.blogspot.com

Show quoteHide quote

"Steve Hershoff" wrote:

> I have two UserControls I'd like to have talk to each other. One of them is
> contained within the other, in a parent/child relationship. The child
> control is loaded dynamically (it's declared as a WebControls.Placeholder)
> in the parent through a call to LoadControl().
>
> I'm using events to communicate between them. The parent will fire an
> event, and if the child is listening it will do something. That's the idea
> at least.
>
>
> In practice I'm having trouble getting the parent's reference while in the
> child. My code looks like this:
>
> public abstract class MyChildControl : System.Web.UI.UserControl {
> .....
> protected MyParentControl parent;
> .....
> parent = (MyParentControl) this.Parent; //big blowup here
> .....
> }
>
> I'm getting an invalid cast error when I call the last line. Obviously I'm
> not clear on how to go about getting a reference to the parent from within
> the child. Could someone show me the proper way of doing this? Thanks very
> much.
>
>
>

31 Jul 2006 2:29 PM

David Jessee

Easiest way I can think of is:

ParentControlType theParent=null;
Control tempControl=this;
while((!tempControl is ParentControlType)&&(!tempControl is Page))
tempControl=tempControl.Parent;
if(tempControl is ParentControlType)
theParent = (ParentControlType)tempControl;

Show quoteHide quote

"Steve Hershoff" wrote:

> I have two UserControls I'd like to have talk to each other. One of them is
> contained within the other, in a parent/child relationship. The child
> control is loaded dynamically (it's declared as a WebControls.Placeholder)
> in the parent through a call to LoadControl().
>
> I'm using events to communicate between them. The parent will fire an
> event, and if the child is listening it will do something. That's the idea
> at least.
>
>
> In practice I'm having trouble getting the parent's reference while in the
> child. My code looks like this:
>
> public abstract class MyChildControl : System.Web.UI.UserControl {
> .....
> protected MyParentControl parent;
> .....
> parent = (MyParentControl) this.Parent; //big blowup here
> .....
> }
>
> I'm getting an invalid cast error when I call the last line. Obviously I'm
> not clear on how to go about getting a reference to the parent from within
> the child. Could someone show me the proper way of doing this? Thanks very
> much.
>
>
>

31 Jul 2006 5:25 PM

Steve Hershoff

This is great-- just what I was looking for. Thanks very much, and thanks
to everyone who replied!

-Steve

Show quoteHide quote

"David Jessee" <DavidJes***@discussions.microsoft.com> wrote in message
news:1B31F947-6F99-4C05-8031-C692E07A552E@microsoft.com...
> Easiest way I can think of is:
>
> ParentControlType theParent=null;
> Control tempControl=this;
> while((!tempControl is ParentControlType)&&(!tempControl is Page))
> tempControl=tempControl.Parent;
> if(tempControl is ParentControlType)
> theParent = (ParentControlType)tempControl;
>
>