实现接口B的接口D的列表无法识别为列表

Question

I have an interface ID, which is derived from another interface IB.

public interface IB
{
    int Num { get; }
}

public interface ID : IB
{

}

Let's say we have a class that implements ID:

public class DImpl : ID
{
     public int Num { get; set; }
}

I know that I can call a function that receives IB with a variable that is held as ID.

public void FuncOfIB(IB b)
{
     // do something
}

public static void Main()
{
     ID d = new DImpl();
     FuncOfIB(d); // Works
}

I would like to call a function that receives a List<IB> as a parameter:

void ProcessListOfIB(List<IB> list)
{
   // Some code
}

But it seems that I can't call this function with List<ID> .

public static void Main()
{
     List<ID> listID = new List<ID>();
     ProcessListOfIB(listID); // Doesn't work
}

Does anyone know why? And how can I fix it? thank you.

Edit: I need the function ProcessListOfIB to remove an item from the list, so copying doesn't solve my problem...

Answer 1

You can create Generic method and limit type to IB:

void ProcessListOfIB<T>(List<T> list) where T:IB
{
    // Some code
}

Answer 2

If you only need to loop through the collection (as opposed to modify it):

void ProcessListOfIB(IEnumerable<IB> list)
{
    // Some code
}

Answer 3

List既未标记为协变也不是协变的（因为它不可能是，它不是接口），所以这就是为什么它不起作用的原因。