The class does not implement the inherited abstract element X, an error in the gics file?

I have a really weird problem with what should be a simple inheritance implementation. During compilation, I get the following error: even after completely cleaning and restoring, and even after completely removing the bin and obj subdirectories:

VideoPlayer1' does not implement inherited abstract member GetShareContent(Windows.ApplicationModel.DataTransfer.DataRequest)
File: VideoPlayer1.g.i.cs

I checked the method signatures between the two classes and they are identical:

public abstract class SharePage : Common.LayoutAwarePage
{
    protected abstract bool GetShareContent(DataRequest request);
}

public sealed partial class VideoPlayer1 : SharePage
{
    protected override bool GetShareContent(DataRequest request)
    {
    }
}   

And I still get the error. The strange thing is that it refers to the generated VideoPlayer1.gics file as the source of the error instead of the main code file, VideoPlayer1.xaml.cs . I've never seen this before.

GetShareContentX(). , , , , .

SO , g.i.cs. - ?