When you implement two interfaces with the same method, how do you know which one is called?

Question

If you have TheMethod() in interfaces I1 and I2, and the following class

class TheClass : I1, I2
{
    void TheMethod()
}

If s

Answer 1

If you instantiate the class, then you are not using any of the interfaces. If you cast the reference to either interface, then you are using that interface. Example:

TheClass c = new TheClass();
c.TheMethod(); // using the class

I1 i = new TheClass();
i.TheMethod(); // using the I1 interface

As your class is declared, both interfaces will use the same method. You can also specify methods for the class and the separate interfaces:

class TheClass : I1, I2
{
  void TheMethod() {} // used by the class
  void I1.TheMethod() {} // used by the I1 interface
  void I2.TheMethod() {} // used by the I2 interface
}

If you specify only methods for the interfaces, you can't reach the method unless you cast the reference to an interface first:

class TheClass : I1, I2
{
  void I1.TheMethod() {} // used by the I1 interface
  void I2.TheMethod() {} // used by the I2 interface
}

If you specify separate methods for only some interfaces, the other interfaces will use the same implementation as the class:

class TheClass : I1, I2
{
  void TheMethod() {} // used by the class and the I1 interface
  void I2.TheMethod() {} // used by the I2 interface
}