Route NotifyPropertyChanged to another class

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Hello,

I have two classes A and B. Both implement INotifyPropertyChanged.
Class B has a property X and Class A has a property of class B.
When X changes, NotifyPropertyChanged fires in class B. How does class A get to know, that X has changed when it has a property of class B? Is there a way to bubble that event up to class A?

public class B : INotifyPropertyChanged
{
	private int x;
	public int X
	{
		get
		{
			return x;
		}
		set
		{
			x = value;
			NotifyPropertyChanged("X"); //this fires
		}
	}
	//Handler and Function for NotifyPropertyChanged not explicitly mentioned....
}

public class A : INotifyPropertyChanged
{
	private B classb;
	public B ClassB
	{
		get
		{
			return classb;
		}
		set
		{
			classb = value;
			NotifyPropertyChanged("ClassB"); //this fires not
		}
	}
	//Handler and Function for NotifyPropertyChanged not explicitly mentioned....
}

Posted 27-Feb-10 23:12pm

Durango66

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4 solutions

Solution 1

INotifyPropertyChanged requires that the class have an event, which I think is called PropertyChanged. Subscribe to that event to be notified when a sub-property changes. Then, in your handler for PropertyChanged, you can fire PropertyChanged in the higher-level class.

Posted 28-Feb-10 0:53am

AspDotNetDev

Solution 2

Yes, this is what all classes implement:

public event PropertyChangedEventHandler PropertyChanged;
        protected void OnPropertyChanged(string propertyName)
        {
            if (this.PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }

So when X changes, OnPropertyChanged of class B gets called and fires the PropertyChanged event. But the higher level class A doesn't get to know anything about this change.

i guess that is because the property of class B changes but not class B itself as property of class A.

Posted 28-Feb-10 1:56am

Durango66

Solution 4

Thank you for your helpful advice.
Now it works properly.

Posted 28-Feb-10 6:11am

Durango66

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AspDotNetDev · Accepted Answer · 2010-02-28T03:39:00

Are you having trouble understanding what I said, or are you just rephrasing it according to your understanding? YES, you can bubble the event up. When A creates an instance of B, it can subscribe to the PropertyChanged event of B so that class A gets notified when its instance of class B has a changed property. When it gets notified of that changed property, it can then subsequently send out a notification itself that the ClassB property was changed. The flow would go like this:

An instance of class B would send a notification that property "X" was changed.
An instance of class A would be notified of the change to property "X".
Upon notification, class A would send out a notification that property "ClassB" was changed.

I hope that makes sense.

Route NotifyPropertyChanged to another class

4 solutions

Solution 3

Solution 1

Solution 2

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