C# Why does calling an interface member from a class generate an error?
- by Jack
So I have an interface:
interface IFoo
{
int Bar();
int this[int i] {get; set;}
}
And a class that derives from it
class Foo : IFoo
{
public int IFoo.Bar()
{
//Implementation
{
public int IFoo.this[int i]
{
//Implementation
}
}
Now, I try to do this:
var fooey = new Foo();
int i = Fooey.Bar();
or this:
int i = Fooey[4];
I would expect these to work properly. However, the compiler generates an error as if such members don't exist. Why is that? I am aware I can cast Foo as IFoo, but I am also aware that casting is costly to performance, which is often the reason to use interfaces in the first place.
EDIT 1:
These are the errors generated
'Foo' does not contain a definition for 'Bar' and no extension method 'Bar' accepting a first argument of type 'Foo' could be found (are you missing a using directive or an assembly reference?)
"Cannot apply indexing to an expression of type 'Foo'"
