Does LINQ work with IEnumerable?

Question

I have a class that implements IEnumerable, but doesn't implement IEnumerable<T>. I can't change this class, and I can't use another class instead of it. As I've understood from MSDN LINQ can be used if class implements IEnumerable<T>. I've tried using instance.ToQueryable(), but it still doesn't enable LINQ methods. I know for sure that this class can contain instances of only one type, so the class could implement IEnumerable<T>, but it just doesn't. So what can I do to query this class using LINQ expressions?

Answer 1

You can use Cast<T>() or OfType<T> to get a generic version of an IEnumerable that fully supports LINQ.

Eg.

IEnumerable objects = ...; IEnumerable<string> strings = objects.Cast<string>(); 

Or if you don't know what type it contains you can always do:

IEnumerable<object> e = objects.Cast<object>(); 

If your non-generic IEnumerable contains objects of various types and you are only interested in eg. the strings you can do:

IEnumerable<string> strings = objects.OfType<string>(); 

Answer 2

Yes it can. You just need to use the Cast<T> function to get it converted to a typed IEnumerable<T>. For example:

IEnumerable e = ...; IEnumerable<object> e2 = e.Cast<object>(); 

Now e2 is an IEnumerable<T> and can work with all LINQ functions.