using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    static void Main(string[] args)

    {

        var a = new Dictionary<string, string>{{"a", "False"}, {"b", "False"}, {"c", "True"}};

        var b = new Dictionary<string, string>{{"a", "False"}, {"b", "True"}, {"c", "False"}};

        var c = a.Except(b).Select(x => x.Key);

        c.Dump();

    }

}