Question

Why does the following not compile?

interface IFoo
{
void Foo();
}

class FooClass : IFoo
{
void IFoo.Foo() { return; }

void Another() {
   Foo();  // ERROR
 }
}

The compiler complains that “The name ‘FooMethod’ does not exist in the current context”.

However, if the Foo method is changed to:

 public void Foo() { return; }

this compiles just fine.

I don’t understand why one works and the other does not.

Answer 1

Because when you “explicitly implement” an interface, you can only access the method by casting to the interface type. Implicit casting will not find the method.

void Another()
{
   IFoo f = (IFoo)this:
   f.Foo();
}

Further reading:

C# Interfaces. Implicit implementation versus Explicit implementation