回顾：Linq To SQL语法 - 实体类

第一篇博客，还望各位大神勿喷

小弟在此代码奉上........

借用NorthWind数据库，实现一个商品展示的小功能。上代码：

添加对Linq的引用

 using System.Data.Linq;//添加对Linq的引用
 using System.Data.Linq.Mapping;//配置对象和映射关系的命名空间

由于图简单，所以写了很少的字段，继续代码

    [Table(Name = "Products")]
    public class Product
    {
        [Column(Name = "ProductID", DbType = "int identity(1,1) not null", IsPrimaryKey = true, IsDbGenerated = true, AutoSync = AutoSync.OnInsert, CanBeNull = true)]
        public int ProductID { get; set; }
        [Column(Name = "ProductName", DbType = "nvarchar(40) not null")]
        public string ProductName { get; set; }
        [Column(Name = "CategoryID", DbType = "int", CanBeNull = true)]
        public int CategoryID { get; set; }
        [Column(Name = "UnitPrice", DbType = "money")]
        public decimal? Price { get; set; }
    }

     [Table(Name = "Categories")]
     public class Categoty
     {
         [Column(Name = "CategoryID", DbType = "int identity(1,1) not null", IsPrimaryKey = true, IsDbGenerated = true, CanBeNull = true, AutoSync = AutoSync.OnInsert)]
         public int ID { get; set; }
         [Column(Name = "CategoryName", DbType = "nvarchar(15) not null")]
         public string CategoryName { get; set; }
         [Column(Name = "Description", DbType = "ntext null")]
         public string Description { get; set; }

         private EntitySet<Products> _products;
         [Association(Name = "C_P", IsForeignKey = false, OtherKey = "CategoryID", ThisKey = "ID", Storage = "_products")]
         public IList<Products> Products
         {
             get { return _products; } //上级接受下级参数，直接返回，上级：Category  下级：Product
             set { _products.Assign(value); }//下级接受上级参数，使用Assign方法进行向上转换
         }
     }

上面分别是两个类：商品类Product与商品类别Category，下面继续创建上下文对象

  public class NorthwindDBContext : DataContext
     {
         private static readonly string conn = ConfigurationManager.ConnectionStrings["Myconn"].ConnectionString;//数据库的连接

         public NorthwindDBContext()
             : base(conn) { }

         public NorthwindDBContext(string connection)
             : base(connection) { }

         public Table<Categoty> Category;

         public Table<Products> Products;
     }

接下来就是展示页面了，创建一个aspx页面吧，扔两个控件上去

 <body>
     <form id="form1" runat="server">
     <div>
         <asp:DropDownList ID="DropDownListCategory" runat="server">
         </asp:DropDownList>
         <asp:Button ID="Button1" runat="server" Text="Button" onclick="Button1_Click" />
         <asp:GridView ID="GridView1" runat="server">
         </asp:GridView>
     </div>
     </form>
 </body>

页面现在也有了，后台代码：

 public partial class ProductsList : System.Web.UI.Page
     {
         Model.NorthwindDBContext db = new Model.NorthwindDBContext();
         protected void Page_Load(object sender, EventArgs e)
         {
             if (!IsPostBack)
             {
                 var query = db.Products.Count();
                 BandCategory();
             }
         }

         private void BandCategory()
         {

             var allCate = from c in db.Catrgorys select c;
             this.DropDownListCategory.DataValueField = "ID";
             this.DropDownListCategory.DataTextField = "Name";
             this.DropDownListCategory.DataSource = allCate;
             this.DropDownListCategory.DataBind();
         }

         protected void Button1_Click(object sender, EventArgs e)
         {
             BandProduct();
         }

         private void BandProduct()
         {

             //生成日志文件，方便程序出错查看生成的SQL语句
             db.Log = new StreamWriter(Server.MapPath("~/log.txt"), true);
             int cid = int.Parse(this.DropDownListCategory.SelectedValue);
             List<Model.Product> lst = db.Products.ToList();
             var Products = db.Products.Where(x => x.CategoryID == cid);
             //拿到类别对象
             //var cate = db.Category.Where(x => x.CategoryID == cid).First();
             this.GridView1.DataSource = Products;//cate.Product;两种方法都行
             this.GridView1.DataBind();
             db.Log.Flush();
             db.Log.Close();

         }

最后效果：

表示刚工作学生路过，大神勿喷...以后会陆续分享一些工作心得的