I’m working through a YouTube example on how to create a login in WPF (MVVM method) using C# via Visual Studios. I’ve gotten thru the second video, but am having the following issues:

Once the proper username and password are entered, the password screen is supposed to close, and a main view window is supposed to open. I am getting the following exception (System.NotImplementedException):

enter image description here

I followed the instructions on the video exactly. The solution explorer files were created according to the video instructions:
enter image description here

namespace WPF_LoginForm;

internal class MainView
{
    public MainView()
    {
    }

    internal void Show() => throw new NotImplementedException();
}```