Question

What is the fastest way to find out whether two ICollection<T> collections contain precisely the same entries? Brute force is clear, I was wondering if there is a more elegant method.

We are using C# 2.0, so no extension methods if possible, please!

Edit: the answer would be interesting both for ordered and unordered collections, and would hopefully be different for each.

Answer 1

use C5

http://www.itu.dk/research/c5/

ContainsAll

‘ Check if all items in a supplied collection is in this bag
(counting multiplicities).
The items to look for.

True if all items are found.’

[Tested]  public virtual bool ContainsAll<U>(SCG.IEnumerable<U> items) where U : T {   HashBag<T> res = new HashBag<T>(itemequalityComparer);    foreach (T item in items)     if (res.ContainsCount(item) < ContainsCount(item))       res.Add(item);     else       return false;    return true; }