Matt Haley Matt Haley - 2 months ago 10
C# Question

Does .NET have a way to check if List a contains all items in List b?

I have the following method:

namespace ListHelper
{
public class ListHelper<T>
{
public static bool ContainsAllItems(List<T> a, List<T> b)
{
return b.TrueForAll(delegate(T t)
{
return a.Contains(t);
});
}
}
}


The purpose of which is to determine if a List contains all the elements of another list. It would appear to me that something like this would be built into .NET already, is that the case and am I duplicating functionality?

Edit: My apologies for not stating up front that I'm using this code on Mono version 2.4.2.

Answer

If you're using .NET 3.5, it's easy:

public static bool ContainsAllItems(List<T> a, List<T> b)
{
    return !b.Except(a).Any();
}

This checks whether there are any elements in b which aren't in a - and then inverts the result.