Doubt regarding interface

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Hi all,

I have a doubt regarding the interface.See the below code

C#

Class sample:IApplication
{
    Test obj = new Test();
    obj.Init(this);
};
Class Test
{
    Public void Init(IApplication app)
    {

    }
}

It is possible to accept as interface object even we are passing this pointer of sample.Please explain how?

Thanks in advance

Posted 24-Nov-11 23:05pm

kutz 2

Updated 24-Nov-11 23:08pm

Mehdi Gholam

v2

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Sergey Alexandrovich Kryukov · Answer 1 · 2011-11-24T23:19:00

This is all about assignment compatibility of types related through inheritance. It does not matter if a base type is an interface or a class, it does not matter if the base is direct or indirect base.

Given a type A is a base type for a type B:

C#

class B : A {/* ... */}

//...

A a = //...
B b = //...
a = b; //you can do it: b is wider than a
//b = a; //you cannot do it

It should be clear why: the compile-time type of b allows to use some members additional to the type A. If second assignment was possible, the attempt to access such member of b would be a disaster, because in actual run-time type of b which actually would be A this member does not exist. The opposite situation (first assignment) does not create any problems.

The conclusion should be apparent to you by now.

—SA