This C# LINQ example shows you how to compare two lists of strings and output those lines that are in names1.txt but not in names2.txt.

// ----------------------------------------------------------------------------
// Find the Set Difference Between Two Lists
// https://msdn.microsoft.com/en-us/library/mt693040.aspx
//
// This example shows how to use LINQ to compare two lists of strings and output
// those lines that are in names1.txt but not in names2.txt.
//
// To create the data files:
//
// Copy names1.txt and names2.txt to your solution folder as shown in
// How to: Combine and Compare String Collections (LINQ) (C#)
// <https://msdn.microsoft.com/en-us/library/mt693089.aspx>
// ----------------------------------------------------------------------------

class CompareLists
{
    static void Main()
    {
        // Create the IEnumerable data sources.
        string[] names1 = System.IO.File.ReadAllLines(@"../../../names1.txt");
        string[] names2 = System.IO.File.ReadAllLines(@"../../../names2.txt");

        // Create the query. Note that method syntax must be used here.
        IEnumerable<string> differenceQuery = names1.Except(names2);

        // Execute the query.
        Console.WriteLine("The following lines are in names1.txt but not names2.txt");
        foreach (string s in differenceQuery)
        {
            Console.WriteLine(s);
        }

        // Keep the console window open in debug mode.
        Console.WriteLine("Press any key to exit");
        Console.ReadKey();
    }
}

/*
    Output:
        The following lines are in names1.txt but not names2.txt
        Potra, Cristina
        Noriega, Fabricio
        Aw, Kam Foo
        Toyoshima, Tim
        Guy, Wey Yuan
        Garcia, Debra
*/