Two interfaces with Same function name

Manoj Bisht · March 25th, 2009, 08:19 AM

I'm executing following program, which is having two interfaces with same function name. So can anybody let me know actually which one or which interface's function is being executed or called

interface intf1
{
void get();
}
interface intf2
{
void get();
}
class A : intf1,intf2
{
public void get()
{
Console.WriteLine("Hello");

}
}

static void Main(string[] args)
{
A e = new A();
e.get();
Console.ReadLine();
}

robzyc · March 25th, 2009, 08:29 AM

I strongly recommend getting "Snippet Compiler" - it rocks at figuring this stuff out for yourself!

Code:

interface IOne
    {
        string GetString();
    }
    interface ITwo
    {
        string GetString();
    }
    
    class CrazyClass : IOne, ITwo
    {
        public string GetString()
        {
            return "some string";
        }
        
        string IOne.GetString()
        {
            return "string for IOne";
        }
        
        string ITwo.GetString()
        {
            return "string for ITwo";
        }
    }
    
    public static void RunSnippet()
    {
        CrazyClass c= new CrazyClass();
        IOne c1 = new CrazyClass();
        ITwo c2 = new CrazyClass();
        WL(c.GetString());
        WL(c1.GetString());
        WL(c1.GetString());
    }

See for yourself!

philip_cole · March 25th, 2009, 08:38 AM

They both are! Because interfaces just say what the method signature (name+parameters+return type) should look like, without any actual logic, it doesn't really matter which one is "executed". The important bit is that A.get() is run.

If one interface returned something different to the other, there is obviously more of a need to know which one to use. As this is impossible to work out however, the code would not compile.

HTH
Phil

robzyc · March 25th, 2009, 08:48 AM

Quote:

Originally Posted by philip_cole

They both are! Because interfaces just say what the method signature (name+parameters+return type) should look like, without any actual logic, it doesn't really matter which one is "executed". The important bit is that A.get() is run.

If one interface returned something different to the other, there is obviously more of a need to know which one to use. As this is impossible to work out however, the code would not compile.

HTH
Phil

Sorry, but this is technically incorrect.. It's not a case of they "both are", rather the ones that satisfy the interface are run.

e.g.

Implicit implementation

public string Get () { ... }

Explicit implementation

string InterfaceA.Get() { ... }
string InterfaceB.Get() { ... }

If implicit, there is only one method to call.

If explicit, then it will call the appropriate type
e.g. InterfaceA mc = new MyClass()
.. Will call the explicit InterfaceA.Get - which can be very different to InterfaceB..

Sorry to split hairs on this, but I think it is important to be clear on the actual behaviour, this kinda stuff can really slip people up! :)
In short

philip_cole · March 25th, 2009, 09:32 AM

Yes you are quite correct Rob, I didn't cross my mind to mention explicit implementation and was just basing it on the implicit code Manoj provided.
In his example, both interfaces have the same method signature, and class A does not provide explicit implementations for both. As you say, with implicit implementation as in this case there is only one method to call, as it satisfies both interfaces, hence my saying "they both are".

robzyc · March 25th, 2009, 09:52 AM

Quote:

Originally Posted by philip_cole

Yes you are quite correct Rob, I didn't cross my mind to mention explicit implementation and was just basing it on the implicit code Manoj provided.
In his example, both interfaces have the same method signature, and class A does not provide explicit implementations for both. As you say, with implicit implementation as in this case there is only one method to call, as it satisfies both interfaces, hence my saying "they both are".

OK cool, it may have just been me misinterpreting what you had said, just thought it might be a good idea to raise it just in case there were any grey areas