String.Join doesn't accept IEnumerable<string>

Question

I have a method with this signature:

IEnumerable<string> GetCombinations(string s, int length)

And I am trying to use it with string.Join like this:

var combinations = GetCombinations(text, 2);
string result = string.Join(", ", combinations);

But I get the following compiler error:

cannot convert from 'System.Collections.Generic.IEnumerable<string>' to 'string[]'

Can't string.Join take an IEnumerable<string>?

Answer 1

What version of the .NET Framework are you using? The overload of String.Join that accepts an IEnumerable instead of an array was added in .NET 4.