What is the relationship between the using keyword and the IDisposable interface?

Question

If I am using the using keyword, do I still have to implement IDisposable?

Answer 1

You can't have one without the other.

When you write :

using(MyClass myObj = new MyClass())
{
    myObj.SomeMthod(...);
}

Compiler will generate something like this :

MyClass myObj = null;
try
{
    myObj = new MyClass();
    myObj.SomeMthod(...);
}
finally
{
    if(myObj != null)
    {
        ((IDisposable)myObj).Dispose();
    }
} 

So as you can see while having using keyword it is assumed/required that IDisposable is implemented.