Question

As the title says: Why does string.Join need to take an array instead of an IEnumerable? This keeps annoying me, since I have to add a .ToArray() when I need to create a joined string from the result of a LINQ expression.

My experience tells me that I’m missing something obvious here.

Answer 1

Upgrade to .NET 4.0 and use the overload that accepts an IEnumerable<string>. Otherwise, just accept that it was a long outstanding problem that wasn’t addressed until .NET 4.0. You can fix the problem by creating your own extension method too!

public static class StringEnumerableExtensions {
    public static string Join(this IEnumerable<string> strings, string separator) {
        return String.Join(separator, strings.ToArray());
    }
}

Usage:

IEnumerable<string> strings;
Console.WriteLine(strings.Join(", "));