Question

I have created a win form solution in C#. The solution has three projects, front layer (FL) business layer (BL) and data layer (DL).

Front layer has all forms. All of the forms implement IForms interface
Business layer has all business logic. All of the business logic classes implement IController interface
Data layer has all data logic that communicates with the sql database. All of the data logic classes inherit IModel interface

I am trying to use MVC design pattern but I am struggling a bit.
Target: Call a method in a class of BL, when I press a button in a form.

If I add BL dll to FL, then I can call the methods of BL.

BL.Class classObject = new BL.Class(this);
classObject.CallMethod();

In the BL, I want to have the reference of the object that called the method so I tried to add reference of the FL dll but it says Circular dll reference.

I want to have a constructor in the BL class:

public BL.Class(IView view)
{
MessageBox(view.Name);
}

How do I architect my solution to achieve this? Please note that the solution is big so I cannot merge all classes into one dll.

Take care,
FM

Answer 1

You can define events in BL for FL to register. Whenever there’s a change in the model, BL should fire an event. It’s up for the view to handle it.

Your BL is created a message box. What if your view is a WebForm? BL shouldn’t know the detail of view.

Also, your BL project shouldn’t have a dll reference to FL. You need to declare IView in BL, not FL.

EDIT:
This is the structure I used before. Your BL defines the interface. Your view has to implement the interface if it wants to use the BL. BL uses the interface to interact with the view. This way, you can build different views that use the same BL.

BL.dll

public interface IView
{
    /// <summary>Update the view</summary>
    void UpdateView(object myBusinessObject);

    /// <summary>Display message</summary>
    void ShowMessage(string msg);
}

public class BL
{
    // Model and View
    private IView _view;

    /// <summary>Constructor</summary>
    public BL (IView view)
    {
        _view = view;
    }

    public void foo()
    {
        // Do something

        // Show message
        _view.ShowMessage("Hello World");
    }
}

FL.dll

public class FL
{
    private BL _myBL;

    /// <summary>Constructor</summary>
    public FL ()
    {
        _myBL = new BL(this);
    }

    /// <summary>Handles user event</summary>
    public void handleEvent()
    {
        // Call BL to do something

        _myBL.foo();
    }

    public void UpdateView(object myBusinessObject)
    {
        // Update your view
    }

    public void ShowMessage(string msg)
    {
        // Display message to user
    }
}