namespace ConsoleApplication35
{
    class Program
    {
        static void Main(string[] args)
        {
            Record Record = new Record();
            Record Record2 = new Record();

            Record.RecordID = 740970205;
            Record.ConnectionID = 1;
            Record2.RecordID = 740970206;
            Record2.ConnectionID = 1;

            int r1 = (Record.ConnectionID + Record.RecordID << 4).GetHashCode(); //получится  -1029378590
            int r2 = (Record2.ConnectionID + Record2.RecordID << 4).GetHashCode(); //получится -1029378574

            Dictionary<int, Record> Dictionary = new Dictionary<int, Record>();

            Dictionary.Add(r1, Record);
            Dictionary.Add(r2, Record2);
        }
    }

    public class Record
    {
        public long RecordID;
        public int ConnectionID;

        public override int GetHashCode()
        {
            return (ConnectionID + RecordID << 4).GetHashCode(); 
        }
    }
}

namespace ConsoleApplication35
{
    class Program
    {
        static void Main(string[] args)
        {
            Record Record = new Record();
            Record Record2 = new Record();

            Record.RecordID = 740970205;
            Record.ConnectionID = 1;
            Record2.RecordID = 740970206;
            Record2.ConnectionID = 1;

            Dictionary<long, Record> Dictionary = new Dictionary<long, Record>();

            Dictionary.Add(Record.RecordID, Record);
            Dictionary.Add(Record2.RecordID, Record2);
        }
    }

    public class Record
    {
        public long RecordID;
        public int ConnectionID;
    }
}