LINQ to SQL之面向对象的添加、查询、更新和删除

介绍
以Northwind为示例数据库，DLINQ(LINQ to SQL)之完全面向对象的添加操作、查询操作、更新操作和删除操作

示例
Sample.aspx

<% @ Page Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeFile=
      "Sample.aspx.cs"
    Inherits="LINQ_DLINQ_Sample" Title="面向对象的添加、查询、更新和删除"  %>

< asp:Content  ID ="Content1"  ContentPlaceHolderID ="head"  runat ="Server" >
asp:Content >
< asp:Content  ID ="Content2"  ContentPlaceHolderID ="ContentPlaceHolder1"  runat ="Server" >
     < p >
        分类名称： < asp:TextBox  ID ="txtCategoryName"  runat ="server" > asp:TextBox >
             分类描述： < asp:TextBox  ID ="txtDescription"  runat ="server" > asp:TextBox >
           
         < asp:Button  ID ="btnAdd"  runat ="server"  Text ="添加"  OnClick ="btnAdd_Click"   />
     p >
     < asp:GridView  ID ="gvCategory"  runat ="server"  DataKeyNames ="CategoryID"
              OnSelectedIndexChanged ="gvCategory_SelectedIndexChanged"         OnRowDeleting ="gvCategory_RowDeleting"  OnRowCancelingEdit ="gvCategory_RowCancelingEdit"
        OnRowEditing ="gvCategory_RowEditing"  OnRowUpdating ="gvCategory_RowUpdating" >
         < Columns >
             < asp:CommandField  ShowSelectButton ="True"  ShowEditButton ="True"
                   ShowDeleteButton ="True" >
             asp:CommandField >
         Columns >
     asp:GridView >
     < br  />
     < asp:DetailsView  ID ="dvProduct"  runat ="server"  DataKeyNames ="ProductID" >
     asp:DetailsView >
asp:Content >

Sample.aspx.cs

using  System;
using  System.Data;
using  System.Configuration;
using  System.Collections;
using  System.Linq;
using  System.Web;
using  System.Web.Security;
using  System.Web.UI;
using  System.Web.UI.WebControls;
using  System.Web.UI.WebControls.WebParts;
using  System.Web.UI.HtmlControls;
using  System.Xml.Linq;

using  DAL;

public  partial  class  LINQ_DLINQ_Sample : System.Web.UI.Page
{
    // 实例化一个NorthwindDataContext（DataContext）
    NorthwindDataContext _ctx = new NorthwindDataContext();

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            BindCategory();
        }
    }

    private void BindCategory()
    {
        // NorthwindDataContext对象的Category属性就是Category集合
        var categories = _ctx.Categories;

        gvCategory.DataSource = categories;
        gvCategory.DataBind();
    }

    protected void btnAdd_Click(object sender, EventArgs e)
    {
        // 实例化一个Category
        Categories c = new Categories();

        // 设置Category对象的相关属性
        c.CategoryName = txtCategoryName.Text;
        c.Description = txtDescription.Text;

        // 使用NorthwindDataContext对象的InsertOnSubmit()方法添加Category对象
        _ctx.Categories.InsertOnSubmit(c);

        // 生成并执行相应的SQL命令
        _ctx.SubmitChanges();

        gvCategory.EditIndex = -1;
        BindCategory();
    }

    protected void gvCategory_SelectedIndexChanged(object sender, EventArgs e)
    {
        // 使用查询语法获得Product集合
        var products = from p in _ctx.Products
                       where p.Categories.CategoryID == (int)gvCategory.SelectedValue
                       select p;

        dvProduct.DataSource = products;
        dvProduct.DataBind();
    }

    protected void gvCategory_RowDeleting(object sender, GridViewDeleteEventArgs e)
    {
        // 使用Single查询操作符获取指定的Category对象
        Categories category = _ctx.Categories.Single(c => c.CategoryID == (int)gvCategory.DataKeys[e.RowIndex].Value);

        // 使用DeleteOnSubmit()方法删除NorthwindDataContext对象的Category集合中的指定Category对象
        _ctx.Categories.DeleteOnSubmit(category);

        // 生成并执行相应的SQL命令
        _ctx.SubmitChanges();

        gvCategory.EditIndex = -1;
        BindCategory();
    }

    protected void gvCategory_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        // 使用查询语法和Single查询操作符获取指定的Category对象
        Categories category = (from c in _ctx.Categories
                             where c.CategoryID == (int)gvCategory.DataKeys[e.RowIndex].Value
                             select c).Single();

        // 设置Category对象的相关属性
        category.CategoryName = ((TextBox)gvCategory.Rows[e.RowIndex].Cells[2].
                 Controls[0]).Text;
        category.Description = ((TextBox)gvCategory.Rows[e.RowIndex].Cells[3].Controls[0]).Text;

        // 生成并执行相应的SQL命令
        _ctx.SubmitChanges();

        gvCategory.EditIndex = -1;
        BindCategory();
    }

    protected void gvCategory_RowEditing(object sender, GridViewEditEventArgs e)
    {
        gvCategory.EditIndex = e.NewEditIndex;
        BindCategory();
    }

    protected void gvCategory_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
    {
        gvCategory.EditIndex = -1;
        BindCategory();
    }
}