Question

I have a ChildUserControl that is loaded inside a ParentUserControl. The host page loads ParentUserControl.

I would need to access properties in ParentUserControl from the ChildUserControl.

Thanks for your time

Answer 1

The platform / language etc isn’t clear, so this answer is necessarily vague… however, in general a child control can’t access properties from the parent (directly), because lots of different types of parent controls could be hosting the child control. The child shouldn’t be hard-coded to a single parent, otherwise it might as well be part of the parent.

Generally, you might want to try to simply remove the requirement – it sounds like an odd design. However, some frameworks support something like this – for example, dependency properties in WPF.

An interface-based design (for the parent(s)) is one approach, but this isn’t very clean. For .NET, events etc are another common way for a child to communicate with a parent – the child exposes events which different parents can consume in different ways.

Other than that, you’re into the territory of testing/casting the parent (either against a class or an interface) to access details from the parent – for example:

ParentControlType parent = this.Parent as ParentControlType; if(parent != null) {     // access properties etc of 'parent' } 

(could also use an interface here; still a bit hacky either way…)

Personally, rather than use this type of cast from the child, I’d prefer the parent to take control; the parent sets properties on the child, and listens to events (rather than the child set properties back on the parent):

// in the parent child.SomeProperty = 132; child.SomePropertyChangd += delegate {     // do something at the parent }; 

This way, the child doesn’t know or care about the parent. All it knows is that it has properties (etc), and can notify other people to interesting changes.