Question

Example:

System.Web.Security.MembershipCollection implements IEnumerable and not IEnumberable<T>. Why doesn’t it implement the latter, when it seems that it would be better (e.g. use LINQ)?

Or, is it not necessarily better?

Answer 1

You can use LINQ with any IEnumerable by using the Cast<T>() function or the OfType<T>() function. If you’re confident that the IEnumerable only contains objects of a particular type, then Cast<T>() will be slightly faster.

For example,

ArrayList foo = new ArrayList();

foo.Add("bar");
foo.Add("baz");

var bar = foo.Cast<string>().Select(s => s.ToUpper());

There are many existing classes (like ArrayList) that existed before the advent of generics in .NET, so they are still non-generic.