Enforce Type constraint when the Type is 'Type'

Question

I want to enforce type constraint when I define a 'type mapping' dictionary, such as this:

internal static class BindingResources
{
    /// 
    /// Key== IDialogWindowVM, Value ==Window
    /// 
    public static readonly Dictionary ViewModelDictionary =
        new Dictionary()
        {
            {typeof(CreateGroupVM), typeof(CreateGroupUI)},
            {typeof(CreateNewNetworkVM), typeof(CreateNewNetwork)}
        };
}

I want to ensure that CreateGroupVM is of the interface IDialogWindowVM, and CreateGroupUI is inherited from Window class. If these conditions are not satisfied that I shall get a compilation error instead of a runtime error.

If this even possible, if yes, how to do it? If no, why?

shingo · Answer

You can use a helper method.

public static Dictionary ViewModelDictionary
{
    get
    {
        var d = new Dictionary();

        void Add()
        where U : IDialogWindowVM
        where V : Window => d.Add(typeof(U), typeof(V));

        Add();
        Add();

        return d;
    }
}

Enforce Type constraint when the Type is 'Type'

1 Answers