Quickest way to find the complement of two collections in C#

Question

I have two collections of type ICollection called c1 and c2. I\'d like to find the set of items that are in c2

Answer 1

public class MyTypeComparer : IEqualityComparer
{
    public MyTypeComparer()
    {    
    }

    #region IComparer Members

    public bool Equals(MyType x, MyType y)
    {
        return string.Equals(x.Id, y.Id);
    }

    public int GetHashCode(MyType obj)
    {
        return base.GetHashCode();
    }

    #endregion     
}

Then, using Linq:

c3 collection = new collection().add(c1);
c3.add(c2);
var items = c3.Distinct(new MyTypeComparer());

You could also do it using generics and predicates. If you need a sample, let me know.