使用GridView分页时，保持内嵌控件状态的技巧。（散分100）

liuyeede 2009-03-10 02:22:47

当时用GridView中使用分页导航到其他页，如果其中内嵌其他控件，比如TextBox、DropDwonList、CheckBox等控件，先前页面的内嵌控件的状态不会保存。当我们返回到先前页面时，仍然会被初始化为默认状态。为了保持我们操作过的内嵌控件的状态。我做了下面的代码，请大家拍砖。如果各位有什么好的方案，可以贴上来，共同学习，共同进步。



<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>



<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">



<html xmlns="http://www.w3.org/1999/xhtml">

<head runat="server">

    <title></title>

</head>

<body>

    <form id="form1" runat="server">

    <div>

        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" 

            PagerSettings-Mode="NumericFirstLast" AllowPaging="True" 

            OnPageIndexChanging="PageIndexChanging" OnPageIndexChanged="PageIndexChanged">



         <Columns>

         <asp:BoundField DataField="CompanyName" HeaderText="公司名称" />

         <asp:BoundField DataField="ContactName" HeaderText="联系人" />

         <asp:BoundField DataField="Phone" HeaderText="联系电话" />   

         <asp:TemplateField HeaderText="测试DropDownList" ShowHeader= "true">

           <ItemTemplate>

            <asp:DropDownList ID="TestDDL" runat="server">

             <asp:ListItem Value="1" Text="One" />             

             <asp:ListItem Value="2" Text="Two"/>

             <asp:ListItem Value="3" Text="Three" />

            </asp:DropDownList>

           </ItemTemplate>

         </asp:TemplateField>     

         </Columns>         

        </asp:GridView>

    </div>

    </form>

</body>

</html>



using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Data;

using System.Data.SqlClient;

using System.Configuration;

/// <summary>

/// 本例以Cache暂存数据，但在实际引用时，建议选用Cookie.

/// </summary>

public partial class _Default : System.Web.UI.Page

{

    public static string sqlStr = "Select CompanyName,ContactName,Phone From Customers";

    public static int allRows = 0;//获取取到数据的总行数；

    protected void Page_Load(object sender, EventArgs e)

    {       

        if (!IsPostBack)

        {

            bind();

        }

    }



    private void bind()

    {

        string connStr = ConfigurationManager.ConnectionStrings["TestSqlConnection"].ConnectionString;



        SqlConnection conn = new SqlConnection(connStr);

        DataSet dt = new DataSet();

        SqlDataAdapter da = new SqlDataAdapter(sqlStr, conn);

        try

        {

            conn.Open();

            da.Fill(dt, "Customers");

            allRows=dt.Tables["Customers"].Rows.Count;

        }

        catch

        {

            throw new ApplicationException("数据库错误");

        }

        finally

        {

            conn.Close();

        }



        this.GridView1.DataSource = dt;

        this.GridView1.DataBind();

    }

    /// <summary>

    /// 判断是否为最后一页，最后一页的行数可能小于指定的PageSize；

    /// </summary>

    /// <returns></returns>

    int CaculateLastRowIndex()

    {

        int ps = this.GridView1.PageSize;

        int pi = this.GridView1.PageIndex;

        return (ps * pi + ps > allRows) ? allRows % ps - 1 : ps - 1;

    }

    /// <summary>

    /// 将DropDrownList的选择项拼接为字符串，保存到Cache中。以"Page"和页面索引PageIndex拼接后的字符串

    /// 作为Cache的存取键。

    /// </summary>

    private void CachDropDownListSelectIndex( )

    {

        string dpl_selectIndexStr =string.Empty;        

        string cacheKey = "Page" + GridView1.PageIndex.ToString();

        for (int i = 0; i <= CaculateLastRowIndex(); i++)

        {

            dpl_selectIndexStr = dpl_selectIndexStr+((DropDownList)(this.GridView1.Rows[i].FindControl("TestDDL"))).SelectedIndex.ToString();

            dpl_selectIndexStr = dpl_selectIndexStr + "|";

        } 

        dpl_selectIndexStr = dpl_selectIndexStr.Substring(0, dpl_selectIndexStr.Length - 1);

        Cache[cacheKey] = dpl_selectIndexStr;     



    }

     /// <summary>

     /// 分解保存的Cache中保存的内嵌控件的状态数据，并恢复。

     /// </summary>

    private void GetCachedDropDownListSelectedIndex( )

    {

        string cacheKey = "Page" + GridView1.PageIndex.ToString();

        if ((Cache[cacheKey] == null)||(Cache[cacheKey].ToString()==string.Empty))

        {

            return;

        }

        string dpl_selectIndexStr = Cache[cacheKey].ToString();    

        string[] selectedIndex = dpl_selectIndexStr.Split('|');

        

        for (int i = 0; i <= CaculateLastRowIndex(); i++)

        {

            ((DropDownList)(this.GridView1.Rows[i].FindControl("TestDDL"))).SelectedIndex = int.Parse(selectedIndex[i]);          

           

        }

        

    }



    protected void PageIndexChanging(object sender, GridViewPageEventArgs e)

    {

        this.CachDropDownListSelectIndex();//换页以前的PageIndex

        GridView1.PageIndex = e.NewPageIndex;        

        bind();

        

    }



    protected void PageIndexChanged(object sender, EventArgs e)

    {      

        this.GetCachedDropDownListSelectedIndex(); //换页以后的PageIndex       

    }

}