Q:

Non-generic IEnumerable to string

There are a lot of questions/answers about conversion from generic IEnumerable to a string.  
But I need a conversion from a non-generic IEnumerable to a string. The result string should be in form of
element1.ToString() + ", " + element2.ToString() + ", " + element3.ToString() + ...
Is there a shorter way than using StringBuilder and looping through the elements by MoveNext()?

A:

You can still use LINQ:
String.Join(", ", thingy.Cast<object>());

