MVC C# - Simplest Possible Implementation

Question

My first try of MVC. Am trying to implement a simple example. Inspiration from here. Have I got this pattern (yet!)?

1. View: "Hey, controller, the user just told me he wants the first person"

2. Controller: "Hmm, having checked his credentials, he is allowed to do that... Hey, model, I want you to get me the first person"

3. Model: "First person... got it. Back to you, Controller."

4. Controller: "Here, I'll collect the new set of data. Back to you, view."

5. View: "Cool, I'll show the first person to the user now."

View:

namespace WinFormMVC
{
    public partial class Form1 : Form
    {
        controller cont = new controller();

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            textBox1.Text = cont.checkPermissionsAndGetFirstPerson();
        }
    }
}

Controller:

public class controller
    {
        public string checkPermissionsAndGetFirstPerson()
        {
            string returnValue = "";
            if (checkPermissions())
            {
                model m = new model();
                returnValue =  m.getFirstPerson();
            }

            return returnValue;

        }

        public bool checkPermissions()
        {
            return true;
        }
    }

Model:

public class model
    {
        public string getFirstPerson()
        {
            return "Bill Smith";
        }
    }

Answer 1

Hmm... I am not sure if I'd call this MVC... As with ASP.NET WebForm, this form is more like an MVP pattern.

As per my understanding, in MVC, controller is the one responsible for managing all resources and flow of the code. In your example, you basically creating a Windows Form first (the view) and then attach a controller to it which is more of a MVP sort of things.

In a classical MVC pattern, the Model, once instantiated, will be linked to the View and when the model changes, the view will get notified (possibly through Observer / PubSub pattern).

Button click, etc. from the View will be routed to the controller which will coordinate those sort of stuffs.

see: this.

Answer 2

I would describe MVC more like this:

1. Request (MVC url routing, some event passed from previous UI etc)

2. Controller - check credentials, get data, return Model

3. Model - represents the data passed back from the Controller

4. View - render the Model returned by the Controller. Depending on the Model may display UI to initialise new Controller actions. May also pass Model back to next Controller action.

I think it can be a little confused because in many Model implementations (such as Linq) they provide data definition and access, but it's still the Controller that knows where to start (even if it's the Model that knows how to save its own changes).

So, your code should be something like:

//Controller:
public class PersonController
{
    public PersonAction Detail(int personId)
    {
        Person returnValue;
        //get person from DB and populate returnValue
        return new PersonAction( returnValue );
    }
}

//Model:
public class Person
{
    public string FirstName {get; set;}
    public string LastName {get; set;}
}

//View:
public partial class PersonDetailView : MVCForm<Person>
{
    public Form1( Person model ):base(model) {
        textBox1.Text = model.FirstName + " " + model.LastName;
    }

    private void button1_Click(object sender, EventArgs e)
    {
        textBox1.Text = model.FirstName + " " + model.LastName;
    }
}

What this example is missing is the framework that makes this all possible - there are two significant parts to that:

1. Something that takes/parses parameters and based on that calls a controller's action method. For instance in Asp.net MVC this is the routing handlers - the call above would be the request url: ~/Person/Detail/personId

2. Something that takes the result from the action (PersonAction in the example above) and finds the correct view to display. In this example it would open a PersonDetailView form and pass the Person model to it.

There are lots of example frameworks for an MVC implementation for WinForms - one of them may be a good starting point.