public class Class1 : IExternalApplication
    {
        public void Execute()
        {
            //Create a list of trans that groupsby same item numbers
            List<Item> lstTrans = Job.Items.Where(x => x.CID == 2).ToList();
            var TransitionGroups = lstTrans.GroupBy(x => x.Number);


            foreach (var TransitionGroup in TransitionGroups)
            {
                var TransitionList = TransitionGroup.ToList();

                foreach (var Trans1 in TransitionList)
                {

                    // Get a list of transitions that does not include the current Trans1
                    var TransitionCompareList = TransitionList.Where(x => x.UniqueId != Trans1.UniqueId).ToList();

                    //Compare Trans1 to Trans2
                    foreach (var Trans2 in TransitionCompareList)
                    {
                        double Trans1Value = Trans1.Dimensions[0].Value + Trans1.Dimensions[1].Value + Trans1.Dimensions[2].Value +
                                             Trans1.Dimensions[3].Value + Trans1.Dimensions[4].Value;
                        double Trans2Value = Trans2.Dimensions[0].Value + Trans2.Dimensions[1].Value + Trans2.Dimensions[2].Value +
                                             Trans2.Dimensions[3].Value + Trans2.Dimensions[4].Value;

                        if (Trans1Value != Trans2Value)
                        {
                            MessageBox.Show("Duplicate Found, Please fix before sending" + "\n" + "Check Item Number: " +
                                             Trans1.Number, "Important Note", MessageBoxButtons.OK, MessageBoxIcon.Exclamation,
                                             MessageBoxDefaultButton.Button1);
                        }
                    }
                }
            }