Explicit Interface Implementation (C# Programming Guide)
If a class implements two interfaces that contain a member with the same signature, then implementing that member on the class will cause both interfaces to use that member as their implementation. In the following example, all the calls to
Paint invoke the same method.
class Test { static void Main() { SampleClass sc = new SampleClass(); IControl ctrl = sc; ISurface srfc = sc; // The following lines all call the same method. sc.Paint(); ctrl.Paint(); srfc.Paint(); } } interface IControl { void Paint(); } interface ISurface { void Paint(); } class SampleClass : IControl, ISurface { // Both ISurface.Paint and IControl.Paint call this method. public void Paint() { Console.WriteLine("Paint method in SampleClass"); } } // Output: // Paint method in SampleClass // Paint method in SampleClass // Paint method in SampleClass:
public class SampleClass : IControl, ISurface { void IControl.Paint() { System.Console.WriteLine("IControl.Paint"); } void ISurface.Paint() { System.Console.WriteLine("ISurface.Paint"); } }
The class member
IControl.Paint is only available through the
IControl interface, and
ISurface.Paint is only available through
ISurface. Both method implementations are separate, and neither is available directly on the class. For example:
// Call the Paint methods from Main. SampleClass obj = new SampleClass(); //obj.Paint(); // Compiler error. IControl c = obj; c.Paint(); // Calls IControl.Paint on SampleClass. ISurface s = obj; s.Paint(); // Calls ISurface.Paint on SampleClass. // Output: // IControl.Paint // ISurface.Paint
Explicit implementation is also used to resolve cases where two interfaces each declare different members of the same name such as a property and a method:
interface ILeft { int P { get;} } interface IRight { int P(); }
To implement both interfaces, a class has to use explicit implementation either for the property P, or the method P, or both, to avoid a compiler error. For example:
class Middle : ILeft, IRight { public int P() { return 0; } int ILeft.P { get { return 0; } } }
See also
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