CODEWITHSUNDEEP
c#classgenericsinheritance
Chris
Chris

Reputation: 788

Create inherited class from type parameter

I have a generic controller to which I pass a class containing only properties. It all works great but...

I want to create another class in the Controller class that inherits the passed class.

Sort of like this:

public class Products
{
    public Int32 ProductID {get; set;}
    public String ProductName {get; set;}
}

public class ProductController : Controller<Products>
{
    public ProductsController() : base("Products", "ProductID", "table", "dbo")
    {
    }
}

public class Controller<T> : IDisposable where T : new()
{
    protected Controller(String tablename, String keyname, String entitytype, String tableschema = "dbo")
    {
        ...
    }

    //How do I create the Recordset class inheriting T
    public class Recordset : T   //<----This is what I don't know how to do
    {
        public Int32 myprop {get; set;}

        public void MoveNext()
        {
            //do stuff
        }
    }
}

How do I create the class Recordset using T as inherited?

Upvotes: 4

Views: 1829

Answers (3)

Blorgbeard
Blorgbeard

Reputation: 103447

The compiler won't let you do that (as I'm sure the error message told you):

Cannot derive from 'identifier' because it is a type parameter
Base classes or interfaces for generic classes cannot be specified by a type parameter. Derive from a specific class or interface, or a specific generic class instead, or include the unknown type as a member.

You could use composition instead of inheritance:

public class Controller<T> : IDisposable where T : new()
{
    public class RecordSet 
    {    
        private T Records;
    
        public RecordSet(T records)
        {
            Records = records;
        }        

        public void MoveNext()
        {
            // pass through to encapsulated instance
            Records.MoveNext();
        }            
    }
}

Upvotes: 6

Chris
Chris

Reputation: 788

public class Controller<T> : IDisposable where T : class, new()
{
    protected Controller(String tablename, String keyname, String entitytype, String tableschema = "dbo")
    {
        ...
    }
   public class Recordset<TT> where TT : class, new()   
    {
        public TT myinheritedclass {get; set}
        public Int32 myprop {get; set;}

        public void MoveNext()
        {
            //do stuff
        }
    }

    public Recordset<T> myRecordset = new Recordset<T>()
}

Upvotes: -1

TakeMeAsAGuest
TakeMeAsAGuest

Reputation: 995

You can do that using classes under Reflection.Emit namespace. but if you are digging that far youll probably find out you dont need inheritence.

Upvotes: 1

Related Questions