What is the best way to check two List<T> lists for equality in C#

Question

There are many ways to do this but I feel like I've missed a function or something.

Obviously List == List will use Object.Equals() and return false.

If every element of the list is equal and present in the same location in the opposite list then I would consider them to be equal. I'm using value types, but a correctly implemented Data object should work in the same fashion (i.e I'm not looking for a shallow copied list, only that the value of each object within is the same).

I've tried searching and there are similar questions, but my question is an equality of every element, in an exact order.

Answer 1

SequenceEqual

Answer 2

Evil implementation is

if (List1.Count == List2.Count)
{
   for(int i = 0; i < List1.Count; i++)
   {
      if(List1[i] != List2[i])
      {
         return false;
      }
   }
   return true;
}
return false;

Answer 3

I knocked up a quick extension method:

namespace ExtensionMethods
{
    public static class MyExtensions
    {
        public static bool Matches<T>(this List<T> list1, List<T> list2)
        {
            if (list1.Count != list2.Count) return false;
            for (var i = 0; i < list1.Count; i++)
            {
                if (list1[i] != list2[i]) return false;
            }
            return true;
        }
    }   
}

Answer 4

I put together this variation:

private bool AreEqual<T>(List<T> x, List<T> y)
{
    // same list or both are null
    if (x == y)
    {
        return true;
    }

    // one is null (but not the other)
    if (x== null || y == null)
    {
        return false;
    }

    // count differs; they are not equal
    if (x.Count != y.Count)
    {
        return false;
    }

    for (int i = 0; i < x.Count; i++)
    {
        if (!x[i].Equals(y[i]))
        {
            return false;
        }
    }
    return true;
}

The nerd in me also crawled out so I did a performance test against SequenceEquals, and this one has a slight edge.

Now, the question to ask; is this tiny, almost measurable performance gain worth adding the code to the code base and maintaining it? I very much doubt it ;o)