private static ConnectionString[] GetConnectionString(Connection[] connections)
        {
            var stringConnection = new ConnectionString[connections.Length];
            for (var i = 0; i < connections.Length; ++i)
            {
                stringConnection[i].Id1 = connections[i].User1Id.ToString();
                stringConnection[i].Id2 = connections[i].User2Id.ToString();
            }

            return stringConnection;
        }
 private static extern IntPtr FindShortestPath(
     ConnectionString[] structs,
     int items,
     string userId1,
     string userId2,
     out int resultArraySize);
 private static extern IntPtr FindMutualFriends(
     ConnectionString[] structs,
     int items,
     string userId1,
     string userId2,
     out int resultArraySize);