Cfrgtkky

So I have run to a problem while trying to follow the MVVM pattern for my WPF project and I spent hours searching for a solution with no luck. The problem is the following: Let's assume that I have a .net Standard library where I have all my view models for my application, for example let's assume that there are the following view models :

BaseDropDownMenuViewModel that inherits from the BaseControlViewModel

AdvancedDropDownMenuViewModel that inherits from the BaseDropDownMenuViewModel

MultiDropDownViewModel that inherits from the AdvancedDropDownViewModel

The view models contain both the functionality of the controls and variables used for their appear for example a BackColor and a ForeColor property that are placed in the BaseControlViewModel. Now ,even though this is sufficient enough for me, I want to add some properties that apply only for desktop platforms, for example a MouseOverBackColor and a MouseOverForeColor property and I also need to be able to override the existing ones ex BackColor. These properties of course would only make sense on desktop platform and not a mobile platform.

Now I have found two solutions for my problem but both of them are not sufficient enough...

• Create a new .net standard library with an interface that forces the implementation of properties available only for desktop applications and create a class for every view model of the base library and implement that interface. In this scenario I will have a huge amount of duplicate code but I will be able to use these classes for my Windows version of my app and the mobile version will not have unused variables for every single one of its controls for example a MouseOverBackColor property that it can't take advantage of.




• Which leads us to my second option which is to implement those properties (MouseOverBackColor,MouseOverForeColor,...) on the BaseControlViewModel on the base .net standard library and have all the versions of my app have those variables even though some might not be able to utilize them. That way I want have duplicate code...

I believe that this problem would be easy to solve if C# supported multi inheritance of classes but since it doesn't I am trying to find another "magic" way of solving this issue. Note: I have also searched about tricks to achieve "multi class inheritance" but those that I was interested in were storing the classes as variables in the main class, which none of this is interests me at the moment because the application would require a massive modification to take advantage of this trick...

You can do this with interfaces:

Example - One class, two interfaces

public interface IDesktopProperties

{

    Color BackColor {get; set;}

    Color MouseOverBackColor {get; set;}

}



public interface IMobileProperties

{

    Color BackColor {get; set;}

    Orientation ScreenOrientation {get; set;}

}



public class MySuperFancyViewModel : IDesktopProperties, IMobileProperties

{

    public Color BackColor {get; set;}

    public Color MouseOverBackColor {get; set;}

    public Orientation ScreenOrientation {get; set;}

}

Now in your Desktop App, you'll have something like

// Will only see properties BackColor and MouseOverBackColor

private IDesktopProperties myProps;

public MyDesktopUI( IDesktopProperties properties ) // <= injected: MySuperFancyViewModel 

{

    myProps = properties;

}

And accordingly for Mobile

// Will only see properties BackColor and ScreenOrientation

private IMobileProperties myProps;

public MyMobileUI( IMobileProperties properties ) // <= injected: MySuperFancyViewModel 

{

    myProps = properties;

}