Convert an interface's event from VB.Net to C#

Question

Hi, I'm struggling to convert the below code to C#.

Class Class1
    Implements IMyInterface

    Public Event MyEvent(ByVal sender As Object, ByVal e As MyEventArgs) Implements IMyInterface.MyEvent

    Public Sub New()
        AddHandler Me.Slider.ValueChanged, AddressOf OnSliderValueChanged
    End Sub

    Private Sub OnSliderValueChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
        RaiseEvent MyEvent(Me, New MyEventArgs())
    End Sub

End Class

Here's what visual studio inserts when I ask it to implement for me:

event EventHandler<MyEventArgs> IMyInterface.MyEvent
    {
        add { throw new NotImplementedException(); }
        remove { throw new NotImplementedException(); }
    }

With a bit of googling I'm sure I can find out what to replace the NotImplementedException parts with but VS is still telling me that the definition is not implemented anyway.

Answer 1

The implementation that Visual Studio creates for you is not a complete implementation, but rather an implementation body which you need to complete. In this case, the lines "throw new NotImplementedException();" need to be replaced by your code.

Answer 2

Using:

http://www.developerfusion.com/tools/convert/vb-to-csharp/

I get:

class Class1 : IMyInterface
{

    public event MyEventEventHandler IMyInterface.MyEvent;
    public delegate void MyEventEventHandler(object sender, MyEventArgs e);

    public Class1()
    {
        this.Slider.ValueChanged += OnSliderValueChanged;
    }

    private void OnSliderValueChanged(System.Object sender, System.EventArgs e)
    {
        if (MyEvent != null) {
            MyEvent(this, new MyEventArgs());
        }
    }

}

Answer 3

Odd that VS generated the add/remove accessors. You don't need them, the compiler automatically generates them. It should look like this:

  public class Class1 : IMyInterface {
    public event EventHandler<MyEventArgs> MyEvent;
    public Class1() {
      this.Slider.ValueChanged += OnSliderValueChanged;
    }
    private void OnSliderValueChanged(object sender, EventArgs e) {
      var handler = MyEvent;
      if (handler != null) {
        handler(this, new MyEventArgs());
      }
    }
  }

Using the "handler" variable avoids a null exception if a thread wires the event.

Edit: ah, it's because you implemented the event explicitly. Not necessary, the event should be public anyway. That's what got you in trouble, the C# syntax diverges here from VB.NET