.NET Junkie

The problem is actually as follows. Let's define a rather awkward generic extension method:

static class IntelliSenseBug_MethodDoesntShowUp
{
    public static void Method<TCollection, TElement>(
        this TCollection collection, TElement element)
        where TCollection : IEnumerable<TElement>
    {
    }
}

The defined extension method has a generic type constrain that states that the TCollection should be a generic IEnumerable interface that contains elements of type TElement. We can use this extension method with like so:

static void Test()
{
    Collection<int> c = new Collection<int>();
    c.Method(1);
}

This all compiles fine, but when typing Test() method's code, you'll notice that after typing c + dot the list of possible operations does not contain our defined 'Method'. The C# compiler is smart enough by using type inference that the passed element is in fact an Int32 and that therefore TElement must be of type Int32 and therefore TCollection must be of type IEnumerable<Int32>. At last the compiler finds out that Collection<int> implements IEnumerable<int> and so it all fits together nicely. Unfortunately IntelliSense isn't as smart as the C# compiler. That's a bummer.

B.t.w. You can read my bug report here.

Update 2008-09-09:
This bug has been fixed in Visual Studio 2008 SP1!

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