Migrate from Basic to MVVM and MEF Composable Patterns for a Silverlight Application - Part 3

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using ProductRiaLib.Web.Services;
using ProductRiaLib.Web.Models;
using System.ComponentModel.Composition;
using ProductApp.Common;

namespace ProductApp.Views
{
    [Export(typeof(IModule)), ExportMetadata(MetadataKeys.Name, ModuleID.ProductListView)]
    public partial class ProductList : UserControl, IModule
    {
        AddProductWindow addProductWindow;
        ProductDomainContext ctx;
        Category comboDefault = new Category{ CategoryID = -1, CategoryName = "Please Select" };
        private bool rowEdited = false;

        public ProductList()
        {
            InitializeComponent();
            
            ctx = new ProductDomainContext();            
            ctx.Load(ctx.GetCategoriesQuery()); 
            ctx.Categories.Add(comboDefault);
            categoryCombo.ItemsSource = ctx.Categories;
            categoryCombo.DisplayMemberPath = "CategoryName";
            categoryCombo.SelectedValuePath = "CategoryID";
            categoryCombo.SelectedIndex = 0;            

            addButton.IsEnabled = false;
            saveButton.IsEnabled = false;
            deleteButton.IsEnabled = false;
        }

        private void addButton_Click(object sender, RoutedEventArgs e)
        {
            List<string> categories = new List<string>();
            
            foreach (var category in ctx.Categories)
            {
                if (category.CategoryID == -1) category.CategoryName = "";
                categories.Add(category.CategoryName);
            }            
            addProductWindow = new AddProductWindow(categories);
            addProductWindow.categoryList.SelectedIndex = categoryCombo.SelectedIndex;            
            addProductWindow.Show();
            addProductWindow.AddEvent += new System.EventHandler(addProductWindow_AddEvent);
        }

        void addProductWindow_AddEvent(object sender, System.EventArgs e)
        {
            AddProductWindow addProductWindow = sender as AddProductWindow;
            Category cat = ctx.Categories.Where(c => c.CategoryName == addProductWindow.SelectedCategory).FirstOrDefault();
            Product p = new Product { ProductName = addProductWindow.ProductName, UnitPrice = addProductWindow.Price, Category = cat };
            ctx.Products.Add(p);
            dataGrid1.SelectedItem = p;
            
            if (this.categoryCombo.Items[0].Equals(comboDefault)) ctx.Categories.Remove(comboDefault);
            ctx.SubmitChanges();
            MessageBox.Show("The product has been added.");            
        }

        private void saveButton_Click(object sender, RoutedEventArgs e)
        {
            if (dataGrid1.SelectedItem != null)
            {
                // Cannot use ctx.HasChanges checker duo to added "Please select" item.
                if (rowEdited)
                {
                    if (this.categoryCombo.Items[0].Equals(comboDefault)) ctx.Categories.Remove(comboDefault);
                    ctx.SubmitChanges();
                    MessageBox.Show("The change has been saved.");                   
                }
            }            
        }

        private void deleteButton_Click(object sender, RoutedEventArgs e)
        {
            if (dataGrid1.SelectedItem != null)
            {
                MessageBoxResult result = MessageBox.Show("Do you really want to delete the product?", "Delete Confirmation", MessageBoxButton.OKCancel);
                if (result == MessageBoxResult.OK)
                {
                    Product deletedProduct = dataGrid1.SelectedItem as Product;
                    ctx.Products.Remove(deletedProduct);
                    
                    //if (this.categoryCombo.Items[0].Equals(comboDefault)) ctx.Categories.Remove(comboDefault);
                    ctx.SubmitChanges();
                    MessageBox.Show("The product has been deleted.");
                }
            }            
        }

        private void categoryCombo_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            ctx.Products.Clear();            
            
            // Reload the data to context based on the selected category
            Category item = (Category)categoryCombo.SelectedItem;
            if (item != null && item.CategoryID > 0)
            {
                ctx.Load(ctx.GetCategorizedProductQuery((int)item.CategoryID)); 
            }
          
            // Rebind the data to DataGrid
            dataGrid1.ItemsSource = ctx.Products;           
            
            addButton.IsEnabled = true;
            saveButton.IsEnabled = false;
            deleteButton.IsEnabled = false;
        }

        private void dataGrid1_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            saveButton.IsEnabled = true;
            deleteButton.IsEnabled = true;            
        }

        private void dataGrid1_RowEditEnded(object sender, DataGridRowEditEndedEventArgs e)
        {
            rowEdited = true;            
        }   
    }
}