Why does the VB.NET compiler think that an interface is not implemented when it is?

Question

Update

I do not think that I was clear enough when I originally posted this question.

Take a look at these screenshots.

( Link to a large screenshot here )

Pay attention to the parts that I put in red. The class shown here executes INotifyPropertyChanged , but the VB compiler seems to believe that the PropertyChanged event declared does not match the INotifyPropertyChanged.PropertyChanged signature.

( Link to a large screenshot here )

Here I selected a line of code violation. Between this and the next screenshot, I literally just cut and pasted the same line back into the file (i.e. I pressed Ctrl + X and then Ctrl + V ).

( Link to a large screenshot here )

Now here! After cutting and pasting the line back, the error disappears.

What's going on here?

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Original question

This happens to me sometimes, especially with the INotifyPropertyChanged interface in my experience, but I have no idea if the problem is limited to this single interface (which would seem strange) or not.

Say I have code like this. There is an interface with a single event. The class implements this interface. It includes an event.

 Public Interface INotifyPropertyChanged Event PropertyChanged As PropertyChangedEventHandler End Interface Public Class Person Implements INotifyPropertyChanged Public Event PropertyChanged _ (ByVal sender As Object, ByVal e As PropertyChangedEventArgs) _ Implements INotifyPropertyChanged.PropertyChanged ' more code below ' End Class 

From time to time, when I build my project, the compiler will suddenly begin to act, like the previous code. It will report that the Person class does not implement INotifyPropertyChanged because it does not have a PropertyChanged event; or he will say that the PropertyChanged event cannot implement INotifyPropertyChanged.PropertyChanged because their signatures do not match.

This is pretty weird, but the weirdest part is here: if I just cut the line starting with Event PropertyChanged and then paste it back in, the error disappears. The project is building.

Does anyone know what can be done here?

Answer 1

The code works fine for me (Visual Studio 2008), you should run into some error.

Anyway, you can also implement it as follows:

 Public Class Person Implements INotifyPropertyChanged Public Event PropertyChanged As PropertyChangedEventHandler _ Implements INotifyPropertyChanged.PropertyChanged End Class 

Answer 2

You need to mark the event Public