How to compare two List to each other? [duplicate]

Answer 1

I discovered that SequenceEqual is not the most efficient way to compare two lists of strings (initially from http://www.dotnetperls.com/sequenceequal).

I wanted to test this myself so I created two methods:

    /// 

    /// Compares two string lists using LINQ's SequenceEqual.
    /// 
    public bool CompareLists1(List list1, List list2)
    {
        return list1.SequenceEqual(list2);
    }

    /// 

    /// Compares two string lists using a loop.
    /// 
    public bool CompareLists2(List list1, List list2)
    {
        if (list1.Count != list2.Count)
            return false;

        for (int i = 0; i < list1.Count; i++)
        {
            if (list1[i] != list2[i])
                return false;
        }

        return true;
    }

The second method is a bit of code I encountered and wondered if it could be refactored to be "easier to read." (And also wondered if LINQ optimization would be faster.)

As it turns out, with two lists containing 32k strings, over 100 executions:

• Method 1 took an average of 6761.8 ticks
• Method 2 took an average of 3268.4 ticks

I usually prefer LINQ for brevity, performance, and code readability; but in this case I think a loop-based method is preferred.

Edit:

I recompiled using optimized code, and ran the test for 1000 iterations. The results still favor the loop (even more so):

• Method 1 took an average of 4227.2 ticks
• Method 2 took an average of 1831.9 ticks

Tested using Visual Studio 2010, C# .NET 4 Client Profile on a Core i7-920