interface ISampleInterface
{
    void SampleMethod();
}

class ImplementationClass : ISampleInterface
{
    // Explicit interface member implementation: 
    void ISampleInterface.SampleMethod()
    {
        // Method implementation.
    }

    static void Main()
    {
        // Declare an interface instance.
        ISampleInterface obj = new ImplementationClass();

        // Call the member.
        obj.SampleMethod();
    }
}

An interface can be a member of a namespace or a class and can contain signatures of the following members:

• Methods

• Properties

• Indexers

• Events

An interface can inherit from one or more base interfaces.

When a base type list contains a base class and interfaces, the base class must come first in the list.

A class that implements an interface can explicitly implement members of that interface. An explicitly implemented member cannot be accessed through a class instance, but only through an instance of the interface.

For more details and code examples on explicit interface implementation, see Explicit Interface Implementation (C# Programming Guide).

The following example demonstrates interface implementation. In this example, the interface contains the property declaration and the class contains the implementation.

interface IPoint
{
   // Property signatures:
   int x
   {
      get;
      set;
   }

   int y
   {
      get;
      set;
   }
}

class Point : IPoint
{
   // Fields:
   private int _x;
   private int _y;

   // Constructor:
   public Point(int x, int y)
   {
      _x = x;
      _y = y;
   }

   // Property implementation:
   public int x
   {
      get
      {
         return _x;
      }

      set
      {
         _x = value;
      }
   }

   public int y
   {
      get
      {
         return _y;
      }
      set
      {
         _y = value;
      }
   }
}

class MainClass
{
   static void PrintPoint(IPoint p)
   {
      Console.WriteLine("x={0}, y={1}", p.x, p.y);
   }

   static void Main()
   {
      Point p = new Point(2, 3);
      Console.Write("My Point: ");
      PrintPoint(p);
   }
}
// Output: My Point: x=2, y=3

For more information, see the following sections in the C# Language Specification:

• 1.9 Interfaces

• 3.4.5 Interface members

• 4.2.4 Interface types

• 10.1.2.2 Interface implementations

• 11.2 Struct interfaces

• 13 Interfaces

Concepts

Reference

Other Resources