Question

I’m trying to create an interface for a model class in ASP.NET MVC2 and I wonder if I can use a List<interface> within another interface. It’s better if I give a code example.

I have two interfaces, a terminal can have multiple bays. So I code my interfaces like the following.

Bay Interface:

public interface IBay
{
    // Properties
    int id {get; set;}
    string name {get;set;}
    // ... other properties
}

Terminal Interface:

public interface ITerminal
{
    // Properties
    int id {get;set;}
    string name {get;set;}
    // ... other properties
    List<IBay> bays {get;set;}
}

My question is when I implement my class based on these interfaces how to I set up the list of bays. Am I going to have to do the list of bays outside the ITerminal interface and inside the concrete implementation?

My goal is to be able to do the following:

Concrete implementation:
Bay Class:

class Bay : IBay
{
    // Constructor
    public Bay()
    {
        // ... constructor
    }
}

Terminal Class:

class Terminal : ITerminal
{
    // Constructor
    public Terminal()
    {
        // ... constructor
    }
}

And then be able to access the list of bays like this

Terminal.Bays

Any help/suggestions would be greatly appreciated.

Answer 1

This should work fine. Just realize that your Terminal class will still contain a List<IBay>, which can be populated with Bay instances as needed. (Note that I would recommend using IList<IBay> instead, however.)

If you want terminal to return a concrete Bay types, then you would need to redesign your Terminal interface, and modify this as:

public interface ITerminal<T> where T : IBay
{
    // Properties
    int Id {get;set;}
    string Name {get;set;}
    IList<T> Bays {get;}
}

public Terminal : ITerminal<Bay>
{
     private List<Bay> bays = new List<Bay>();
     IList<Bay> Bays { get { return bays; } }
     // ...
     public Terminal()
     {
         bays.Add(new Bay { //...

However, there may be little value in adding this complexity.