如何强制一个类实现从特定基类/接口（而不是特定类型）派生的属性

Question

In my solution, there are a number of classes C1 , C2 , C3 etc. that all inherit from a common abstract base class CB .

There are also a number of classes D1 , D2 , D3 etc. that act as a data-source for the corresponding C class (eg the data-source for C1 is a local property of type D1 etc). The D classes all inherit from a common abstract base class DB , but vary in their implementation (both inherited and non-inherited properties & methods are used by the C class).

Now, I want to impose a rule that all C classes (ie that derive from CB ) must implement a "data-source" property, and the type of this property must be derived from DB .

My initial idea was to do this:

public abstract class CB
{
    protected abstract DB DataSource { get; set; } 

    etc.
}

However, this means that the overridden DataSource property in the C classes can only be of type DB , not a type derived from DB .

How can I impose my rule? Ideally CB and DB would remain abstract base classes (because there are non-abstract properties and methods in each that I wish the C and D classes to inherit), but they could be converted to interfaces if needed. However I think I have exactly the same problem if I do that.

Answer 1

You're looking for generic class:

public abstract class CB<T> where T : DB
{
    protected abstract T DataSource { get; set; } 

    etc
}

Now, C1 should be defined as:

public class C1 : CB<D1>
{
    protected override D1 DataSource { get; set; }
}