asp.net ajax技巧7

  继续读老章的书，这次是看到如何在一个master页面中放些按钮，然后点的时候，更新content页面中的东西，而且可以做到局部更新。先看主MASTER页面
master页面的前台
<form id="form1" runat="server">
        <div>
            <asp:ScriptManager ID="ScriptManager1" runat="server" />
            <asp:Panel ID="MasterPanel1" runat="server" GroupingText="主控页面">
               <asp:Button ID="MasterButton1" runat="server" Text="整页更新" />
               <asp:Button ID="MasterButton2" runat="server" Text="局部更新" OnClick="MasterButton2_Click" Width="128px" />
            </asp:Panel>
            <asp:ContentPlaceHolder ID="ContentPlaceHolder1" runat="server">
            </asp:ContentPlaceHolder>
        </div>
master页面的后台

 protected void Page_Load(object sender, EventArgs e)
    {
        ScriptManager1.RegisterAsyncPostBackControl(MasterButton2);
    }

    public DateTime LastUpdate
    {
        get
        {
            if(ViewState["LastUpdate"] == null)
            {
                return DateTime.Now;
            }
            else
            {
                return Convert.ToDateTime(ViewState["LastUpdate"]);
            }
        }
        set
        {
            ViewState["LastUpdate"] = value;
        }
    }

    protected void MasterButton2_Click(object sender, EventArgs e)
    {
        LastUpdate = DateTime.Now;
        UpdatePanel up1 = (UpdatePanel)(ContentPlaceHolder1.FindControl("UpdatePanel1"));
        up1.Update();
    }

注意这里因为希望主页面的“局部更新”按钮能引发异步更新内容页面中的UPDATEPANEL控件的内容，因此必须用
        ScriptManager1.RegisterAsyncPostBackControl(MasterButton2);
注册该按钮引发的事件。
   要注意masterbutton2_click事件的写法，调用内容页中的updatepanel控件的UPDATE方法来更新内容。
然后在内容页中前台中

<%@ Page Language="C#" MasterPageFile="~/ThirdMasterPage.master" AutoEventWireup="true"
    CodeFile="CH3_DemoForm040.aspx.cs" Inherits="CH3_DemoForm040" Title="如何于主控页面中使用 UpdatePanel 控件" %>

<%@ MasterType VirtualPath="ThirdMasterPage.master" %>
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
    <asp:Panel ID="Panel2" GroupingText="内容页面" runat="server">
        <asp:UpdatePanel ID="UpdatePanel1" UpdateMode="Conditional" runat="server">
            <ContentTemplate>
                <p>
                    上一次更新：<strong><%= Master.LastUpdate.ToString() %></strong></p>
                <asp:Button ID="ContentButton" OnClick="ContentButton_Click" runat="server" Text="局部更新">
                </asp:Button>
            </ContentTemplate>
        </asp:UpdatePanel>
    </asp:Panel>
</asp:Content>

后台中，为其“局部更新”编写相关的事件，以将当前日期时间给主控页面的lastupdate属性
protected void ContentButton_Click(object sender, EventArgs e)
    {
        Master.LastUpdate = DateTime.Now;
    }