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:

 


<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:


<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:


<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 />

                            <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:

 


<%@ 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>

        &nbsp;</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="

                            <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:https://files.cnblogs.com/Terrylee/ASPNETAJAXUpdatePanelDemo2.rar