8、步步为营VS 2008 + .NET 3.5(8) - DLINQ(LINQ to SQL)之面向对象的添加、查询、更新和删除

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步步为营VS 2008 + .NET 3.5(8) - DLINQ(LINQ to SQL)之面向对象的添加、查询、更新和删除

作者：webabcd


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>
        &nbsp;&nbsp; 分类描述：<asp:TextBox ID="txtDescription" runat="server"></asp:TextBox>
        &nbsp;&nbsp;
        <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();
    }
}

OK
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