How to setup polymorphic classes and recursion with C#? - c#-4.0

Question

A base class, VideoContainer, contains a list of VideoContainers.
The properties in VideoContainer are common to three other classes of which there are three:
Layout
Perspective
Source
Each of these classes have different properties, and should fit inside the VideoContainers collection.
/// <summary>
/// Video container
/// </summary>
public class VideoContainer<T>
{
/// <summary>
/// Container ID
/// </summary>
public int Id { get; set; }
/// <summary>
/// Type of container - {Layout, Perspective, SourceContainer}
///
/// This is usually set by the instantiated class.
/// </summary>
public ContainerTypes ContainerType { get; set; }
/// <summary>
/// Parent ID
/// </summary>
public VideoContainerIdentifier ParentObject { get; set; }
/// <summary>
/// Name of container
/// </summary>
public string Name { get; set; }
/// <summary>
/// Details about the physical location of this container
/// </summary>
public LocationDefinition LocationDefinition { get; set; }
/// <summary>
/// When container has a tile applied - number of rows of containers within this perspective
/// </summary>
public short NumRows { get; set; }
/// <summary>
/// When container has a tile aplpied - the number of columns of containers within this perspective
/// </summary>
public short NumColumns { get; set; }
/// <summary>
/// List of containers
/// </summary>
public IList<VideoContainer<T>> VideoContainers { get; set; }
/// <summary>
/// Draw
/// </summary>
public virtual void Draw()
{
// drawing tasks
}
}
The initial problem was that I couldn't put a Layout (or other class type) inside the VideoContainers collection, as it expects a type of VideoContainer.
So I added <T>, hoping but having problems accessing the properties of type <T> - which doesn't work.
How can I set this up properly?
-- UPDATE --
What I forgot to mention is that the classes all inherit VideoContainers.
As per the suggestion below, I created public interface IVideoContainer<T>.
The Layout class is now defined as public class Layout : IVideoContainer<Layout> and implements all of the interface's methods:
public class Layout : IVideoContainer<Layout>
{
/// <summary>
/// ctor
/// </summary>
public Layout()
{
ContainerType = ContainerTypes.Layout;
}
public int Id
{...
Problem is in implementing:
var layout = new IVideoContainer<Layout>
{
Id = 1,
ParentObject = null,
Name = "Layout Definition 1",
LocationDefinition = new LocationDefinition
{
TopLeftX = 0,
TopLeftY = 0,
WidthPixels = 1000,
HeightPixels = 1000
},
NumRows = 20,
NumColumns = 20,
VideoContainers = new List<Perspective>
{
new IVideoContainer<Perspective>
{
Id = 10, ...
-- Update 2 --
I now have:
/// <summary>
/// VideoContainer
/// </summary>
/// <typeparam name="T"></typeparam>
public class VideoContainer<T> : IVideoContainer
{
public int Id { get; set; }
public ContainerTypes ContainerType { get; set; }
public VideoContainerIdentifier ParentObject { get; set; }
public string Name { get; set; }
public LocationDefinition LocationDefinition { get; set; }
public short NumRows { get; set; }
public short NumColumns { get; set; }
public IList<IVideoContainer> VideoContainers { get; set; }
}
The issue is that SourceContainer contains new properties, which I cannot access - CctvId and StreamUri:
VideoContainers = new List<VideoContainer<SourceContainer>>
{
new VideoContainer<SourceContainer>
{
Id = 20,
ParentObject = new VideoContainerIdentifier
{
Id = 10,
ContainerType = ContainerTypes.Perspective
},
ContainerType = ContainerTypes.SourceContainer,
CctvId = new Guid(),
StreamUri = new Uri("http://127.0.0.1/somestream"),
LocationDefinition = new LocationDefinition // TODO: verify that {x,y} are relative to the perspective
{
TopLeftX = 0,
TopLeftY = 0,
WidthPixels = 10,
HeightPixels = 10
}
},
SourceContainer class:
public class SourceContainer : IVideoContainer
{
/// <summary>
/// the URI of the stream for this source
/// </summary>
public Uri StreamUri { get; set; }
/// <summary>
/// the descriptive name of this source
/// </summary>
//public string Name { get; set; }
/// <summary>
/// optional device id for this source
/// </summary>
public Guid? CctvId { get; set; }
/// <summary>
/// ctor
/// </summary>
public SourceContainer()
{
ContainerType = ContainerTypes.SourceContainer;
}
public int Id { get; set; }
public ContainerTypes ContainerType { get; set; }
public VideoContainerIdentifier ParentObject { get; set; }
public string Name { get; set; }
public LocationDefinition LocationDefinition { get; set; }
public short NumRows { get; set; }
public short NumColumns { get; set; }
public IList<IVideoContainer> VideoContainers { get; set; }
}

Answer 1

Create an Interface that collects the common properties, have your three classes inherit from it, and then cast your T to the Interface to access the properties.
public class VideoContainer: IVideoContainer
{
public List<IVideoContainer> Children { get; set; }
}
If you want to access properties specific to the object you're storing in the List, just cast it to the original object:
var child = Children.First();
var type = m.GetType();
if(type.Name == "ChildClass")
{
var container = (ChildClass)child;
// Now you can access VideoContainer specific properties in `container`.
}