ASP.NET AJAX入门系列（5）：使用UpdatePanel控件（二）

最新推荐文章于 2019-08-10 00:11:56 发布

powerboy

最新推荐文章于 2019-08-10 00:11:56 发布

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分类专栏： AJAX 文章标签： asp.net ajax asp server button triggers

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UpdatePanel 可以用来创建丰富的局部更新Web应用程序，它是ASP.NET 2.0 AJAX Extensions中很重要的一个控件，其强大之处在于不用编写任何客户端脚本，只要在一个页面上添加几个UpdatePanel控件和一个ScriptManager控件就可以自动实现局部更新。通过本文来学习一下UpdatePanel其他的一些使用方法（第二篇）。

主要内容

1 ．用编程的方法控制UpdatePanel的更新

2 ．UpdatePanel的嵌套使用

3 ．同一页面上使用多个UpdatePanel

一．用编程的方法控制UpdatePanel的更新

对于UpdatePanel，我们也可以使用编程的方法来控制它的更新，可以通过ScriptManager的RegisterAsyncPostBackControl()方法注册一个异步提交的控件，并且调用UpdatePanel的Update()方法来让它更新。再次用我在前面的文章中用到的一个无聊的时间更新例子来看一下，有时候我觉得例子过于复杂更加不好说明白所要讲的内容，如下代码所示，注意Button1并不包含在UpdatePanel中：

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

< script runat ="server" >

void Button1_Click(object sender, EventArgs e)

{

this.Label2.Text = DateTime.Now.ToString();

}

</ script >

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

< head runat ="server" >

< title > Refreshing an UpdatePanel Programmatically </ title >

</ head >

< body >

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

< asp:ScriptManager ID ="ScriptManager1" runat ="server" />

< div >

< asp:UpdatePanel ID ="UpdatePanel1" runat ="server" UpdateMode ="Conditional" >

< ContentTemplate >

< asp:Label ID ="Label1" runat ="server" Text ="更新时间：" ></ asp:Label >

< asp:Label ID ="Label2" runat ="server" Text ="Label" ForeColor ="Red" ></ asp:Label >< br />< br />

</ ContentTemplate >

</ asp:UpdatePanel >

< asp:Button ID ="Button1" runat ="server" Text ="Button" OnClick = "Button1_Click" />

</ div >

</ form >

</ body >

</ html >

这时候不用多说，肯定是整页提交了，运行如下图所示：

再次修改上面的例子，使用ScriptManager的RegisterAsyncPostBackControl()注册Button1为一个异步提交控件，并且调用UpdatePanel的Update()方法：

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

< script runat ="server" >

void Page_Load(object sender, EventArgs e)

{

ScriptManager1.RegisterAsyncPostBackControl(Button1);

}

void Button1_Click(object sender, EventArgs e)

{

this.Label2.Text = DateTime.Now.ToString();

this.UpdatePanel1.Update();

}

</ script >

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

< head runat ="server" >

< title > Refreshing an UpdatePanel Programmatically </ title >

</ head >

< body >

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

< asp:ScriptManager ID ="ScriptManager1" runat ="server" />

< div >

< asp:UpdatePanel ID ="UpdatePanel1" runat ="server" UpdateMode ="Conditional" >

< ContentTemplate >

< asp:Label ID ="Label1" runat ="server" Text ="更新时间：" ></ asp:Label >

< asp:Label ID ="Label2" runat ="server" Text ="Label" ForeColor ="Red" ></ asp:Label >< br />< br />

</ ContentTemplate >

</ asp:UpdatePanel >

< asp:Button ID ="Button1" runat ="server" Text ="Button" OnClick = "Button1_Click" />

</ div >

</ form >

</ body >

</ html >

这时候可以看到，已经是异步提交了：

二． UpdatePanel的嵌套使用

UpdatePanel 还可以嵌套使用，即在一个UpdatePanel的ContentTemplate中还可以放入另一个UpdatePanel。当最外面的UpdatePanel被触发更新时，它里面的子UpdatePanel也随着更新，里面的UpdatePanel触发更新时，只更新它自己，而不会更新外层的UpdatePanel。看下面的例子：

<% @ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %>

< script runat ="server" >

</ script >

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

< head id ="Head1" runat ="server" >

< title > UpdatePanelUpdateMode Example </ title >

< style type ="text/css" >

div.NestedPanel

{

position: relative;

margin: 2% 5% 2% 5%;

}

</ style >

</ head >

< body >

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

< div >

< asp:ScriptManager ID ="ScriptManager"

runat ="server" />

< asp:UpdatePanel ID ="OuterPanel"

UpdateMode ="Conditional"

runat ="server" >

< ContentTemplate >

< div >

< fieldset >

< legend > Outer Panel </ legend >

< br />

< asp:Button ID ="OPButton1"

Text ="Outer Panel Button"

runat ="server" />

< br />

Last updated on

<% = DateTime.Now.ToString() %>

< br />

< asp:UpdatePanel ID ="NestedPanel1"

UpdateMode ="Conditional"

runat ="server" >

< ContentTemplate >

< div class ="NestedPanel" >

< fieldset >

< legend > Nested Panel 1 </ legend >

< br />

Last updated on

<% = DateTime.Now.ToString() %>

< br />

< asp:Button ID ="NPButton1"

Text ="Nested Panel 1 Button"

runat ="server" />

</ fieldset >

</ div >

</ ContentTemplate >

</ asp:UpdatePanel >

</ fieldset >

</ div >

</ ContentTemplate >

</ asp:UpdatePanel >

</ div >

</ form >

</ body >

</ html >

运行后如下：

三．同一页面上使用多个UpdatePanel

使用UpdatePanel的时候并没有限制在一个页面上用多少个UpdatePanel，所以我们可以为不同的需要局部更新的页面区域加上不同的UpdatePanel。由于UpdatePanel默认的UpdateMode是Always，如果页面上有一个局部更新被触发，则所有的UpdatePanel都将更新，这是我们不愿看到的，我们只需要UpdatePanel在它自己的触发器触发的时候更新就可以了，所以需要把UpdateMode设置为Conditional。

来看一下官方网站上提供的一个例子：包括两个UpdatePanel，其中一个用来用户输入而另一个则用来显示数据，每一个UpdatePanel的UpdateMode属性都设置为Conditional。当我们单击Cancel按钮时，只有用来用户输入的那个UpdatePanel刷新，当单击Insert按钮时，两个UpdatePanel都刷新。代码如下：

<% @ Page Language="C#" %>

<% @ Import Namespace="System.Collections.Generic" %>

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

< head id ="Head1" runat ="server" >

< title > Enter New Employees </ title >

< script runat ="server" >

private List<Employee> EmployeeList;

protected void Page_Load()

{

if (!IsPostBack)

{

EmployeeList = new List<Employee>();

EmployeeList.Add(new Employee(1, "Jump", "Dan"));

EmployeeList.Add(new Employee(2, "Kirwan", "Yvette"));

ViewState["EmployeeList"] = EmployeeList;

}

else

EmployeeList = (List<Employee>)ViewState["EmployeeList"];

EmployeesGridView.DataSource = EmployeeList;

EmployeesGridView.DataBind();

}

protected void InsertButton_Click(object sender, EventArgs e)

{

if (String.IsNullOrEmpty(FirstNameTextBox.Text) ||

String.IsNullOrEmpty(LastNameTextBox.Text)) { return; }

int employeeID = EmployeeList[EmployeeList.Count-1].EmployeeID + 1;

string lastName = Server.HtmlEncode(FirstNameTextBox.Text);

string firstName = Server.HtmlEncode(LastNameTextBox.Text);

FirstNameTextBox.Text = String.Empty;

LastNameTextBox.Text = String.Empty;

EmployeeList.Add(new Employee(employeeID, lastName, firstName));

ViewState["EmployeeList"] = EmployeeList;

EmployeesGridView.DataBind();

EmployeesGridView.PageIndex = EmployeesGridView.PageCount;

}

protected void CancelButton_Click(object sender, EventArgs e)

{

FirstNameTextBox.Text = String.Empty;

LastNameTextBox.Text = String.Empty;

}

[Serializable]

public class Employee

{

private int _employeeID;

private string _lastName;

private string _firstName;

public int EmployeeID

{

get { return _employeeID; }

}

public string LastName

{

get { return _lastName; }

}

public string FirstName

{

get { return _firstName; }

}

public Employee(int employeeID, string lastName, string firstName)

{

_employeeID = employeeID;

_lastName = lastName;

_firstName = firstName;

}

</ script >

</ head >

< body >

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

< div >

  </ div >

< asp:ScriptManager ID ="ScriptManager1" runat ="server" EnablePartialRendering ="true" />

< table >

< tr >

< td style ="height: 206px" valign ="top" >

< asp:UpdatePanel ID ="InsertEmployeeUpdatePanel" runat ="server" UpdateMode ="Conditional" >

< ContentTemplate >

< table cellpadding ="2" border ="0" style ="background-color:#7C6F57" >

< tr >

< td >< asp:Label ID ="FirstNameLabel" runat ="server" AssociatedControlID ="FirstNameTextBox"

Text ="First Name" ForeColor ="White" /></ td >

< td >< asp:TextBox runat ="server" ID ="FirstNameTextBox" /></ td >

</ tr >

< tr >

< td >< asp:Label ID ="LastNameLabel" runat ="server" AssociatedControlID ="LastNameTextBox"

Text ="Last Name" ForeColor ="White" /></ td >

< td >< asp:TextBox runat ="server" ID ="LastNameTextBox" /></ td >

</ tr >

< tr >

< td ></ td >

< td >

< asp:LinkButton ID ="InsertButton" runat ="server" Text ="Insert" OnClick ="InsertButton_Click" ForeColor ="White" />

< asp:LinkButton ID ="Cancelbutton" runat ="server" Text ="Cancel" OnClick ="CancelButton_Click" ForeColor ="White" />

</ td >

</ tr >

</ table >

< asp:Label runat ="server" ID ="InputTimeLabel" > <% = DateTime.Now %> </ asp:Label >

</ ContentTemplate >

</ asp:UpdatePanel >

</ td >

< td style ="height: 206px" valign ="top" >

< asp:UpdatePanel ID ="EmployeesUpdatePanel" runat ="server" UpdateMode ="Conditional" >

< ContentTemplate >

< asp:GridView ID ="EmployeesGridView" runat ="server" BackColor ="LightGoldenrodYellow" BorderColor ="Tan"

BorderWidth ="1px" CellPadding ="2" ForeColor ="Black" GridLines ="None" AutoGenerateColumns ="False" >

< FooterStyle BackColor ="Tan" />

< SelectedRowStyle BackColor ="DarkSlateBlue" ForeColor ="GhostWhite" />

< PagerStyle BackColor ="PaleGoldenrod" ForeColor ="DarkSlateBlue" HorizontalAlign ="Center" />

< HeaderStyle BackColor ="Tan" Font-Bold ="True" />

< AlternatingRowStyle BackColor ="PaleGoldenrod" />

< Columns >

< asp:BoundField DataField ="EmployeeID" HeaderText ="Employee ID" />

< asp:BoundField DataField ="LastName" HeaderText ="Last Name" />

< asp:BoundField DataField ="FirstName" HeaderText ="First Name" />

</ Columns >

< PagerSettings PageButtonCount ="5" />

</ asp:GridView >

< asp:Label runat ="server" ID ="ListTimeLabel" > <% = DateTime.Now %> </ asp:Label >

</ ContentTemplate >

< Triggers >

< asp:AsyncPostBackTrigger ControlID ="InsertButton" EventName ="Click" />

</ Triggers >

</ asp:UpdatePanel >

</ td >

</ tr >

</ table >

</ form >

</ body >

</ html >

运行后效果如下：

示例代码下载