AddRange to a Collection

There are some similar questions to this; I did not find one that I felt answered this use case. (Please feel free to correct me!)

A coworker asked me today how to add a range to a collection. He has a class that inherits from Collection<T>. There's a get-only property of that type that already contains some items. He wants to add the items in another collection to the property collection. How can he do so in a C#3-friendly fashion? (Note the constraint about the get-only property, which prevents solutions like doing Union and reassigning.)

Sure, a foreach with Property.Add will work. But a List<T>-style AddRange would be far more elegant.

It's easy enough to write an extension method:

public static class CollectionHelpers
{
    public static void AddRange<T>(this ICollection<T> destination,
                                   IEnumerable<T> source)
    {
        foreach (T item in source)
        {
            destination.Add(item);
        }
    }
}

But I have the feeling I'm reinventing the wheel. I didn't find anything similar in System.Linq or morelinq.

Bad design? Just Call Add? Missing the obvious?

Thanks!

From stackoverflow

• No, this seems perfectly reasonable. There is a List<T>.AddRange() method that basically does just this, but requires your collection to be a concrete List<T>.

  TrueWill : Thanks; very true, but most public properties follow the MS guidelines and are not Lists.

  Reed Copsey : Yeah - I was giving it more as rationale for why I don't think there is a problem with doing this. Just realize it will be less efficient than the List version (since the list can pre-allocate)

• The C5 Generic Collections Library classes all support the AddRange method. C5 has a much more robust interface that actually exposes all of the features of its underlying implementations and is interface-compatible with the System.Collections.Generic ICollection and IList interfaces, meaning that C5's collections can be easily substituted as the underlying implementation.