c# wpf keyinput DeadCharProcessed

public static Key RealKey(this KeyEventArgs e)
{
    switch (e.Key)
    {
        case Key.System:
            return e.SystemKey;

        case Key.ImeProcessed:
            return e.ImeProcessedKey;

        case Key.DeadCharProcessed:
            return e.DeadCharProcessedKey;

        default:
            return e.Key;
    }
}