Linq to sql 的DataContext 持久化层写法

//web.config 页面 

<connectionStrings>
    <add name="admin" connectionString="Data Source=(local)\MSSQLSERVER2008;Initial Catalog=USBbuilding;User ID=liuming;Password=111111" providerName="System.Data.SqlClient"/>
  </connectionStrings>

// 创建连接数据库

public  class conn
    {
        public static SqlConnection GetSqlconn()
        {
            SqlConnection sqlconn = new SqlConnection(ConfigurationManager.ConnectionStrings["admin"].ConnectionString);
            return sqlconn;
        }
    }

//linq to model层，拖入表格进去

//页面添加按钮

<asp:Button ID="Button1" runat="server" Text="提 交" onclick="Button1_Click" />           
<asp:Button ID="Button2" runat="server" Text="编 辑" onclick="Button2_Click" /> 

//CS页面代码

  protected void Button1_Click(object sender, EventArgs e)
        {
            TableDataContext Tdc = new TableDataContext();  

            Tdc.addD_News.Title = title.Text;
            Tdc.addD_News.Author = author.Text;
            Tdc.addD_News.CopyFrom = copyfrom.Text;
            Tdc.addD_News.CreateTime =Convert.ToDateTime(createtime.Text);
            Tdc.addD_News.Contented = contented.Value;

            if (CheckBox1.Checked == true)
            {
                Tdc.addD_News.State = "1";
            }
            else
            {
                Tdc.addD_News.State = "0";
            }
            Tdc.addD_News.Droped = false;          
            Tdc.D_NewsTable().InsertOnSubmit(Tdc.addD_News);
            Tdc.Dc.SubmitChanges();
            JudgJavaScript.Alert("添加成功");

        }

protected void Button2_Click(object sender, EventArgs e)
        {
            TableDataContext Tdc = new TableDataContext();     
            var uptheid = Tdc.D_NewsTable().Single(i => i.Id == int.Parse(hidid.Value));
                 uptheid.Title = title.Text;
                 uptheid.Title = title.Text;
                 uptheid.Author = author.Text;
                 uptheid.CopyFrom = copyfrom.Text;
                 uptheid.CreateTime = Convert.ToDateTime(createtime.Text.ToString());
                 uptheid.Contented = contented.Value;

                 if (CheckBox1.Checked == true)
                 {
                     uptheid.State = "1";
                 }
                 else
                 {
                     uptheid.State = "0";
                 }

            Tdc.Dc.SubmitChanges();
            JudgJavaScript.Alert("修改成功");
        }

//这里，你注意"TableDataContext Tdc = new TableDataContext();  "

public  DataContext Dc = new DataContext(conn.GetSqlconn());

      //---- D_News 数据表;
       public D_News addD_News =new D_News();   
       public Table<D_News> D_NewsTable()
       {
           Table<D_News> table=Dc.GetTable<D_News>();
           return table;
       }

// 上面就是数据库表，持久层，以后对Linq的DataContext 可以重复使用了。