No generic implementation of OrderedDictionary?

Question

I'm using .NET 3.5. I think I know the answer to this, but am looking for confirmation so should be a quick one!

There doesn't appear to be a generic implementation of OrderedDictionary (which is in System.Collections.Specialized namespace). Is there one that I'm missing?

I've found implementations out there to provide the functionality, but wondered if/why there isn't a generic implementation out-of-the-box and if anyone knows whether it's something in .NET 4.0?

Answer 1

You're right. There's no generic equivalent of OrderedDictionary in the framework itself.

(That's still the case for .NET4 too, as far as I'm aware.)

Answer 2

There surely is no generic version of this because it would need a generic comparer implemented. The OrderedDictionary could be ordered, because the type of objects is known through its definition and therefore a comparer for those types can be implemented directly.

Butyou can use the generic dictionary, provide an IComparer object to it and sort it like needed -> at last with extension method .OrderBy(). This flexibilty is needed, since the IComparer must be generic for the same type as the dictionary.