Compare two List<string> using LINQ in C#

Question

What is the best way to compare two lists based on values, order and the number of values. So all of the lists below should be different.

var list1 = new List<string> { "1", "2" };
var list2 = new List<string> { "2", "1" };
var list3 = new List<string> { "1", "2", "3" };

Answer 1

How about using SequenceEqual.

See http://ideone.com/yZeYRh

var a = new [] { "1", "2", "3" };
var b = new [] { "1", "2" };
var c = new [] { "2", "1" };

Console.WriteLine(a.SequenceEqual(b)); // false
Console.WriteLine(a.SequenceEqual(c)); // false
Console.WriteLine(c.SequenceEqual(b)); // false

It comes from the namespace System.Linq and can be used on any IEnumerable.

You can also pass it an IEqualityComparer to for example also do:

var d = new [] { "a", "B" };
var e = new [] { "A", "b" };

Console.WriteLine(d.SequenceEqual(e, StringComparer.OrdinalIgnoreCase)); // true

Answer 2

I like Zip for this, but you still need to manually compare Count.

lista.Count() ==listb.Count() && lista.Zip(listb, Equals).All(a=>a);