Learning C# 3.0

Explicit Interface Implementation

In the implementation shown so far, the class that implements the interface (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 Document is implementing IStorable, for example; the compiler understands this implicitly.

What happens, however, if the class implements two interfaces, each of which has a method with the same signature? This might happen if the class implements interfaces defined by two different organizations or even two different programmers. The next example creates two interfaces: IStorable and ITalk. ITalk 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( )

Marking the Read( ) method as a member of the ITalk interface resolves the conflict between the identical Read( ) methods. There are some additional aspects you should keep in mind.

First, 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 ...