Nunit Assertion for an empty intersection between collection

I've looked all around, and can't quite figure this one out, and my multitude of trial and error attempts have all been useless.

I have a list of user names (we'll call 'o开发者_JAVA百科riginal list') one object is returning I have a list of user names (we'll call 'filtration list') another object is returning

I am testing a method that returns all of the items from the original list not in the filtration list.

Ideally what I want is something like

Assert.That(returnedList, Has.No.Members.In(filtrationList))

So far the only thing I can do is iterate over the filtrationList and do

Assert.That(returnedList, Has.None.EqualTo(filteredUser))

With nunit you can create any custom constraint. If you want to verify two collections for intersection, you can create something like this:

public class Intersects : CollectionConstraint
{
    private IEnumerable _collection2;

    public Intersects(IEnumerable collection2)
        : base(collection2)
    {
        _collection2 = collection2;
    }

    public static Intersects With(IEnumerable arg)
    {
        return new Intersects(arg);
    }

    protected override bool doMatch(IEnumerable collection)
    {
        foreach (object value in collection)
        {
            foreach (object value2 in _collection2)
                if (value.Equals(value2))
                    return true;
        }

        return false;
    }

    public override void WriteDescriptionTo(MessageWriter writer)
    {
        //You can put here something more meaningful like items which should not be in verified collection.
        writer.Write("intersecting collections");
    }
}

usage is pretty simple:

string[] returnedList = new string[] { "Martin", "Kent", "Jack"};
List<string> filteredUsers = new List<string>();
filteredUsers.Add("Jack");
filteredUsers.Add("Bob");
Assert.That(returnedList, Intersects.With(filteredUsers));