Nested Interfaces: Cast IDictionary> to IDictionary>?

Question

I would think it\'s fairly straightforward to cast an IDictionary> object to an IDictionary

Answer 1

This may or may not help you, but I thought I'd throw it out as a supplement to Jon's answer.

If all you need is the dictionary's values, without reference to their keys, you can do this:

IDictionary> dictionary = Whatever();
var values = (IEnumerable>)dictionary.Values;

For this to work, you must be using C# 4.0 or later, and TValue must be constrained to be a reference type. Here's the code, slightly refactored, and with comments to explain:

IDictionary> dictionary = Whatever();

//Values returns an ICollection>
ICollection> temp1 = dictionary.Values;

//ICollection inherits from IEnumerable
IEnumerable> temp2 = temp1;

//IEnumerable is covariant
//There is an implicit reference conversion between IList and IEnumerable
//So there is an implicit reference conversion between IEnumerable>
//and IEnumerable>
IEnumerable> values = temp2;