Question

I have an Interface called as IObSrc, I have few classes that implement this interface called as ObSrc1, ObScr2 etc..

Interface IObSrc
{
  string id;
}

I also have an interface called as IDtSrc, this interface inturn is implemented by a few classes called as DtSrc1, DtSrc2.

Interface IDtSrc
{
  IObSrc getObject();
  Dictionary<string,IObSrc> getObjects();
}

When i implement this interface from DtSrc1, and I return ObSrc1 from DtSrc1, there is no issue, but when i return Dictionary<string,ObSrc1> or Dictionary<string,ObSrc2>, i get an indication of typemismatch.

public class DtSrc : IDtSrc
{
  public Dictionary<string,IObSrc> getObjects()
  {
    Dictionary<string,ObSrc1> val1 = new ...'
    ...
    return val1;
  }

}

How can i solve this issue.

* EDITED *

I have one more query, what if a method should return a generic type that can be varied by the implementation.

Example:

interface IDtSrc<T> where T:IObSrc
{ 
  T ExecuteObject(string objId);
}

This will be used as

class DtSrc1 
{ 
  string ExecuteObject(string objId)
  {..}
}

and

class DtSrc2
{ 
 Dictionary<string,string> ExecuteObject(string objId)
 {..}
}

Kindly suggest a right procedure for this also.

Answer 1

You could use generics with a constraint

interface IDtSrc<T> where T:IObSrc
{
  IObSrc getObject();
  Dictionary<string,T> getObjects();
}

But your implementation of IDtSrc will only be able to return one type of IObSrc.