Entity Framework- Databinding with WinForms

文献参考

微软EF官方文档

实现IBindList接口

using System.Collections;using System.Collections.ObjectModel;using System.ComponentModel;using System.Data.Entity;namespace WinFormWithEF.Lib{    /// <summary>    /// ObservableListSource    /// </summary>    public class ObservableListSource<T> : ObservableCollection<T>, IListSource    where T : class    {        private IBindingList _bindingList;        bool IListSource.ContainsListCollection { get { return false; } }        IList IListSource.GetList()        {            return _bindingList ?? (_bindingList = this.ToBindingList());        }    }}

定义模型

运用Code first，首先创建两个实体，Category实体和product实体，它们是一对多的关系。

namespace WinFormWithEF.Entity{    /// <summary>    /// Category    /// </summary>    public class Category    {        private readonly ObservableListSource<Product> _products = new ObservableListSource<Product>();        public int CategoryId { get; set; }        public string Name { get; set; }        public virtual ObservableListSource<Product> Products { get { return _products; } }    }}

Product实体：

namespace WinFormWithEF.Entity{    /// <summary>    /// Product    /// </summary>    public class Product    {        public int ProductId { get; set; }        public string Name { get; set; }        public int CategoryId { get; set; }        public virtual Category Category { get; set; } //navigation property    }}

除了定义实体类外，还需要定义一个继承于 DbContext的类，暴露 DbSet<TEntity> 属性。 DbSet属性使得上下文知道你想要什么类型包括在模型中。

这个 Dbset 实例管理运行时的对象，包括从数据库中获取数据填充到对象，更改跟踪，持久化数据到数据库。

添加一个 ProductContext 类：

using System.Data.Entity;namespace WinFormWithEF.Entity{    /// <summary>    /// ProductContext    /// </summary>    public class ProductContext : DbContext    {        public DbSet<Category> Categories { get; set; }        public DbSet<Product> Products { get; set; }    }}

绑定对象到控件

vs2010中，选择数据->添加新数据源，如下图所示，选择对象，点击下一步，

选择对应文件夹下的 Category，如下图所示，然后保存。

绑定控件

将选择好的数据源拖拽到窗体的grid上，分别选择 Category对象上图，Product 对应下表格。为 保存添加相应handler，总的代码如下：

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Data.Entity;using System.Drawing;using System.Linq;using System.Text;using System.Windows.Forms;using WinFormWithEF.Entity;namespace WinFormWithEF{    public partial class Form1 : Form    {        ProductContext _context;        public Form1()        {            InitializeComponent();        }        protected override void OnLoad(EventArgs e)        {            base.OnLoad(e);            _context = new ProductContext();            // Call the Load method to get the data for the given DbSet             // from the database.             // The data is materialized as entities. The entities are managed by             // the DbContext instance.             _context.Categories.Load();            // Bind the categoryBindingSource.DataSource to             // all the Unchanged, Modified and Added Category objects that             // are currently tracked by the DbContext.            // Note that we need to call ToBindingList() on the             // ObservableCollection<TEntity> returned by            // the DbSet.Local property to get the BindingList<T>            // in order to facilitate two-way binding in WinForms.            this.categoryBindingSource.DataSource =                _context.Categories.Local.ToBindingList();        }        private void categoryBindingNavigatorSaveItem_Click(object sender, EventArgs e)        {            this.Validate();            // Currently, the Entity Framework doesn’t mark the entities             // that are removed from a navigation property (in our example the Products)            // as deleted in the context.             // The following code uses LINQ to Objects against the Local collection             // to find all products and marks any that do not have            // a Category reference as deleted.             // The ToList call is required because otherwise             // the collection will be modified             // by the Remove call while it is being enumerated.             // In most other situations you can do LINQ to Objects directly             // against the Local property without using ToList first.            foreach (var product in _context.Products.Local.ToList())            {                if (product.Category == null)                {                    _context.Products.Remove(product);                }            }            // Save the changes to the database.            this._context.SaveChanges();            // Refresh the controls to show the values                     // that were generated by the database.            this.categoryDataGridView.Refresh();            this.productsDataGridView.Refresh();        }        protected override void OnClosing(CancelEventArgs e)        {            base.OnClosing(e);            this._context.Dispose();        }    }}

点击保存。

查看数据库sql express