LinQ SO Question

public partial class CircuitInstallationScheduledWindow : Window
    {
        DataSet mainWorkbook, Access;
        string tSubject, tCC, tHTML;
        DataTable previewTable;
        public CircuitInstallationScheduledWindow(DataSet mainWorkbook, string tSubject, string tCC, string tHTML)
        {
            this.tSubject = tSubject;
            this.tCC = tCC;
            this.tHTML = tHTML;
            this.mainWorkbook = mainWorkbook;
            InitializeComponent();
            Access = ABFS_Database.getTables();
            previewTable = MakePreview();
            previewGrid.ItemsSource = previewTable.AsDataView();



        }
        public DataTable MakePreview()
        {
            //gets all rows from the "Salesforce Report Weekly" sheet with FOC dates which are today or in the future.
            var table = (from row in mainWorkbook.Tables["Salesforce Report Weekly"].AsEnumerable()
                         where row.Field<DateTime?>("Target Circuit Completion (FOC)") >= DateTime.Today
                         select row).AsDataView().ToTable(false, "Opportunity: Store Number", "Target Circuit Completion (FOC)", "Vendor Name");

            //gets all rows from the ALreadySent table where the Notification Type is "Install Scheduled".
            var sentCIS = (from row in Access.Tables["AlreadySent"].AsEnumerable()
                           where row.Field<string>("NotificationType") == "Install Scheduled"
                           select row).AsDataView().ToTable();
            //filters out rows in 'table' which were already sent and recorded in the Access database.
            var filteredTable = table.AsEnumerable()
                .Where(t1 => !sentCIS.AsEnumerable()
                    .Any(t2 => t2.Field<int>("StoreNumber") == t1.Field<double>("Opportunity: Store Number")
                            && Math.Abs((t2.Field<DateTime>("TargetCircuitCompletionFOC") - t1.Field<DateTime>("Target Circuit Completion (FOC)")).TotalDays)<1)).AsDataView().ToTable();
            //join filtered table with McDonalds Contact Master.
            var contacts = mainWorkbook.Tables["MCD Contact Master"].AsDataView().ToTable(false, "National Store .","Contacts - ACM - Email", "OO - Ops Mgr Name",
                                                                                    "OO - Ops Mgr Name", "Contacts - Area Sup / BC - Email", "Contacts - OTP - Email", "OTM Email Address");
            DataTable resultTable = new DataTable();
            foreach(string name in new string[]{"Opportunity: Store Number", "Target Circuit Completion (FOC)", "Vendor Name","Contacts - ACM - Email", "OO - Ops Mgr Name", "OO - Ops Mgr Name", "Contacts - Area Sup / BC - Email", "Contacts - OTP - Email", "OTM Email Address"})
            {
                resultTable.Columns.Add(name);
            }

            var joinedTables =  from tableRow in filteredTable.AsEnumerable()
                                join contactsRow in contacts.AsEnumerable()
                                on tableRow.Field<double>("Opportunity: Store Number") equals contactsRow.Field<double>("National Store .")
                                into lj
                                from r in lj.DefaultIfEmpty()
                                select resultTable.LoadDataRow(new object[]
                                {
                                    tableRow.Field<double>("Opportunity: Store Number"),
                                    tableRow.Field<DateTime>("Target Circuit Completion (FOC)"),
                                    tableRow.Field<string>("Vendor Name"),
                                    contactsRow.Field<string>("Contacts - ACM - Email")
                                }, false);




        }
    }