OOP design and Lists and collections (C#)

Question

Hello guys,

I need to design a simple piece of software, and i was wondering the best to do it.

First of all, sorry for the novice question: what is the best way to work with lists? i tried a few times and did not perceived the correct way to instanciate them and how to use them in OOP. Can anyone clear it up for me?

The second question is: i have the following classes (loosely formatted, not code)

Tenement:
tenementID Int32,
polygons Polygon, (here i need to use a list, but how?)
status TenementStatus;

Polygon:
polygonID Int32,
vertexes vertex (need to use a list here too),
areaPolygon;

Vertex:
vertexID Int32,
X Int32,
Y Int32;

Is my idea of these classes correct? Is there an easier way to do this?

Answer 1

Well in C# a List is simply a data structure representing a collection of objects that can be accessed by index. If that sentence makes sense, you understand pretty much all you need to know about lists (for this example at least). If not, you might start by taking a look at the MSDN documentation for the List(T) class.

Example:

// Declare a new list of vertices
List<Vertex> vertices = new List<Vertex>();

// Add a couple of vertices
vertices.Add(new Vertex(0, 0, 0));
vertices.Add(new Vertex(1, 100, 100));
vertices.Add(new Vertex(2, 50, 50));

// Get a vertex back out of the list by using its index
Vertex temp = vertices[1]; // this is the second vertex we added above

Answer 2

In C#, you'll want to use the List<T> class to work with collections that are lists.

For example:

public class Tenement
{
     public Tenement()
     {
         this.Polygons = new List<Polygon>(); // Create the list here...
     }
     public int Id { get; set; }
     public IList<Polygon> Polygons { get; private set; }
     // ...

Edit: If you need to control how items are added or removed, such as checking to make sure the polygon is valid, you could also do:

public class Tenement
{
     public Tenement()
     {
         this.polygons = new List<Polygon>(); // Create the list here...
     }
     private List<Polygon> polygons;

     public int Id { get; set; }
     public IEnumerable<Polygon> Polygons { 
        get { return this.polygons; }
     }
     public void AddPolygon(Polygon polygon) {
         // Do extra stuff here, then:
         this.polygons.Add(polygon);
     }
     // ...

Answer 3

If you're looking for a simple List object...

List<Vertex> vertices = new List<Vertex>();

and

List<TenementStatus> statuses = new List<TenementStatus>();

That's the simple declaration for your needs...