Question

I have a very simple class that has a single property and which inherits INotifyPropertyChanged:

class SimpleClass:INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    private string _property;
    public string Property
    {
        get { return _property; }
        set
        {
            _property = value; 
            PropertyChanged(this, new PropertyChangedEventArgs"Property"));
        }
    }
}

I try to instantiate a SimpleClass object in the constructor for a WPF Window but I get the following TargetInvocationException: “Exception has been thrown by the target of an invocation”.
If I remove the INotifyPropertyChange inheritance (and any reference to the PropertyChanged event) then I don’t get the error and my project runs without any problems. Any ideas why?

Cheers

Answer 1

You aren’t checking for null on PropertyChanged.

if nobody is listening, then it will be null. most people protect for the event listeners to change during the event, as well:

var listeners = PropertyChanged;
if (listeners != null)
    listeners(this, new PropertyChangedEventArgs("Property");