Created forms to allow the management of ad items, suppliers and ad special keywords. Updated the database migration tool to include the ad special table. Cleaned up the main form's code and did a slight touch up of the interface.

AdvertsingProfitControl/FrmManageSuppliers.cs

@@ -0,0 +1,180 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Data;
+using System.Data.Entity.Infrastructure;
+using System.Drawing;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Transactions;
+using System.Windows.Forms;
+
+namespace AdvertsingProfitControl
+{
+    public partial class FrmManageSuppliers : Form
+    {
+        private bool _isUpdating;
+
+        public FrmManageSuppliers()
+        {
+            InitializeComponent();
+            newSupplierTextBox.TextChanged += UpdateButtonOnTextChanged;
+            suppliersListBox.ItemSelectionChanged += UpdateSupplierFields;
+            var columnHeader = new ColumnHeader
+            {
+                Name = "SupplierHeaderColumn",
+                Width = Width / 2
+            };
+            suppliersListBox.Columns.Add(columnHeader);
+            RefreshSupplierListing();
+        }
+
+        private void UpdateSupplierFields(object sender, ListViewItemSelectionChangedEventArgs e)
+        {
+            newSupplierTextBox.Text = ((Supplier)e.Item.Tag).Name;
+            descriptionTextBox.Text = ((Supplier)e.Item.Tag).Description;
+            _isUpdating = true;
+            deleteSupplierButton.Enabled = true;
+            registerSupplierButton.Text = @"Update Supplier";
+            newSupplierLabel.Text = @"Update Supplier:";
+        }
+
+        private void UpdateButtonOnTextChanged(object sender, EventArgs e)
+        {
+            if (_isUpdating && newSupplierTextBox.Text.Length == 0)
+            {
+                _isUpdating = false;
+                descriptionTextBox.Text = string.Empty;
+                registerSupplierButton.Text = @"Register Supplier";
+                newSupplierLabel.Text = @"Register New Supplier:";
+            }
+            registerSupplierButton.Enabled = newSupplierTextBox.Text.Length > 0;
+        }
+
+        private void RefreshSupplierListing()
+        {
+            suppliersListBox.Items.Clear();
+            var db = new AdvertisingProfitControlModel();
+            var suppliers = db.Suppliers.Select(x => x).OrderBy(x => x.Name);
+            var supplierCount = 0;
+            foreach (var supplier in suppliers)
+            {
+                var item = new ListViewItem
+                {
+                    Text = supplier.Name,
+                    Tag = supplier
+                };
+                suppliersListBox.Items.Add(item);
+                supplierCount++;
+            }
+
+            suppliersListBox.Columns[0].Text = supplierCount > 0 ? @"Current Suppliers:" : @"No Suppliers to Display";
+            deleteSupplierButton.Enabled = false;
+            newSupplierTextBox.Text = string.Empty;
+            descriptionTextBox.Text = string.Empty;
+        }
+
+        private void registerSupplierButton_Click(object sender, EventArgs e)
+        {
+            var db = new AdvertisingProfitControlModel();
+            if (!_isUpdating)
+            {
+                if (!db.Suppliers.Any(x => x.Name == newSupplierTextBox.Text))
+                {
+                    var supplier = new Supplier()
+                    {
+                        Name = newSupplierTextBox.Text,
+                        Description = descriptionTextBox.Text
+                    };
+                    db.Suppliers.Add(supplier);
+                    try
+                    {
+                        db.SaveChanges();
+                        informationLabel.Text = @"Registered '" + Environment.NewLine + supplier.Name + Environment.NewLine + @"' successfully.";
+                    }
+                    catch (DbUpdateException ex)
+                    {
+                        informationLabel.Text = @"Failed to register '" + Environment.NewLine + supplier.Name + @"'." + Environment.NewLine +
+                                                ex.Message;
+                    }
+                }
+                else
+                {
+                    MessageBox.Show(@"Supplier '" + newSupplierTextBox.Text + @"' already exists.",
+                        @"Duplicate Entry", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
+                    newSupplierTextBox.Text = string.Empty;
+                }
+            }
+            else
+            {
+                var item = suppliersListBox.SelectedItems[0];
+                var index = ((Supplier)item.Tag).Id;
+                var supplier = db.Suppliers.SingleOrDefault(x => x.Id == index);
+                if (supplier == null)
+                {
+                    informationLabel.Text = @"Failed to retrieve " + Environment.NewLine + @"supplier ID.";
+                    return;
+                }
+                supplier.Name = newSupplierTextBox.Text;
+                supplier.Description = descriptionTextBox.Text;
+                db.SaveChanges();
+                informationLabel.Text = @"Updated '" + Environment.NewLine + newSupplierTextBox.Text + Environment.NewLine + @"' successfully.";
+            }
+            RefreshSupplierListing();
+        }
+
+        private void deleteSupplierButton_Click(object sender, EventArgs e)
+        {
+            var item = suppliersListBox.SelectedItems[0];
+            var oldSupplier = (Supplier)item.Tag;
+            var db = new AdvertisingProfitControlModel();
+            var supplier = db.Suppliers.Single(x => x.Id == oldSupplier.Id);
+            //Check to see if the ad special is used by other tables.
+            if (supplier.Invoices.Count > 0)
+            {
+                //If so, display a warning to the user about the potential data loss.
+                var result =
+                    MessageBox.Show(
+                        supplier.Invoices.Count +
+                        @" reference(s) to this supplier found. Do you want to delete these records? This can not be undone.",
+                        @"References to " + oldSupplier.Name + @" Found", MessageBoxButtons.YesNoCancel,
+                        MessageBoxIcon.Question);
+                if (result != DialogResult.Yes) return;
+                //Perform the necessary operations to remove all references to the key word.
+                using (var scope = new TransactionScope())
+                {
+                    try
+                    {
+                        db.Invoices.RemoveRange(db.Invoices.Where(x => x.FkSupplierId == oldSupplier.Id));
+                        db.Suppliers.Remove(supplier);
+                        db.SaveChanges();
+                        scope.Complete();
+                        informationLabel.Text = @"Removed '" + Environment.NewLine + oldSupplier.Name +
+                                                Environment.NewLine + @"' successfully.";
+                    }
+                    catch (DbUpdateException ex)
+                    {
+                        informationLabel.Text = @"Failed to remove " + Environment.NewLine + oldSupplier.Name + @"." +
+                                                Environment.NewLine + ex.Message;
+                    }
+                }
+            }
+            else
+            {
+                try
+                {
+                    db.Suppliers.Remove(supplier);
+                    db.SaveChanges();
+                    informationLabel.Text = @"Removed '" + Environment.NewLine + oldSupplier.Name +
+                                            Environment.NewLine + @"' successfully.";
+                }
+                catch (DbUpdateException ex)
+                {
+                    informationLabel.Text = @"Failed to remove " + Environment.NewLine + oldSupplier.Name + @"." + Environment.NewLine + ex.Message;
+                }
+            }
+            RefreshSupplierListing();
+        }
+    }
+}