Programming C#, Second Edition

Explicit Interface Implementation

In the implementation shown so far, the implementing class (in this case, Document) creates a member method with the same signature and return type as the method detailed in the interface. It is not necessary to explicitly state that this is an implementation of an interface; this is understood by the compiler implicitly.

What happens, however, if the class implements two interfaces, each of which has a method with the same signature? Example 8-5 creates two interfaces: IStorable and ITalk. The latter implements a Read( ) method that reads a book aloud. Unfortunately, this conflicts with the Read( ) method in IStorable.

Because both IStorable and ITalk have a Read( ) method, the implementing Document class must use explicit implementation for at least one of the methods. With explicit implementation, the implementing class (Document) explicitly identifies the interface for the method:

void ITalk.Read( )

This resolves the conflict, but it does create a series of interesting side effects.

First, there is no need to use explicit implementation with the other method of Talk:

public void Talk( )

Because there is no conflict, this can be declared as usual.

More importantly, the explicit implementation method cannot have an access modifier:

void ITalk.Read( )

This method is implicitly public.

In fact, a method declared through explicit implementation cannot be declared with the abstract, virtual, override, or new modifiers.

Most important, you cannot access ...