Question

I’m really new to OOP and C# and I’m trying to understand, how I could write my code as DRY as possible. In my ASP.NET MVC 3 Application I have multiple actions (two in this example code) in a controller which all return a different ViewModel which are all inheriting the same BaseViewModel. This is because I need the same data on every action but with additional properties for each.

I know I could simply create a constructor for ActionOneViewModel which receives a ViewModel object. But is this the common way to do this? Or are there any alternatives?

View Models:

class BaseViewModel 
{
    public string Name { get; set; }
    public List<User> Users { get; set; }
}

class ActionOneViewModel : BaseViewModel 
{
    public bool FooBar { get; set; }
}

class ActionTwoViewModel : BaseViewModel 
{
    public string PingPong { get; set; }
}

Controller Actions:

public ActionResult ActionOne () 
{
    // this doesn't work (of course)
    ActionOneViewModel model = (ActionOneViewModel)createViewModel();
    model.FooBar = true;

    return View(model);
}

public ActionResult ActionTwo () 
{
    // this doesn't work (of course)
    ActionTwoViewModel model = (ActionTwoViewModel)createViewModel();
    model.PingPong = "blub";

    return View(model);
}

private BaseViewModel createViewModel()
{
    BaseViewModel model = new BaseViewModel();

    //
    // doing a lot of stuff here
    //

    return model;
}

Answer 1

How about:

ActionTwoViewModel model = new ActionTwoViewModel();
model = createViewModel(model);


private BaseViewModel createViewModel(BaseViewModel model)
{
    //
    // doing a lot of stuff here
    //

    return model;
}