通过

PostBackTrigger 类

  • 参考

定义

命名空间:
System.Web.UI
程序集:
System.Web.Extensions.dll

将 UpdatePanel 控件内部的控件定义为回发控件。

public ref class PostBackTrigger : System::Web::UI::UpdatePanelControlTrigger
public class PostBackTrigger : System.Web.UI.UpdatePanelControlTrigger
type PostBackTrigger = class
    inherit UpdatePanelControlTrigger
Public Class PostBackTrigger
Inherits UpdatePanelControlTrigger
继承
Object
UpdatePanelTrigger
UpdatePanelControlTrigger
PostBackTrigger

示例

以下示例演示如何以声明方式定义 PostBackTrigger 控件 UpdatePanel 的控件。 在面板中，控件 FileUpload 允许用户上传文件。 用户必须首先检查要上传的文件是否存在。 Button调用事件处理程序以检查文件名的控件会导致异步回发。 但是， Button 上传文件的控件注册为一个 PostBackTrigger，因为无法异步上传文件。

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

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

<script runat="server">

    private string saveDir = @"Uploads\";
    
    protected void UploadButton_Click(object sender, EventArgs e)
    {
        if (FileUpload1.HasFile && FileUpload1.FileBytes.Length < 10000 &&
            !CheckForFileName())
        {
            string savePath = Request.PhysicalApplicationPath + saveDir +
                Server.HtmlEncode(FileName.Text);
            //Remove comment from the next line to upload file.
            //FileUpload1.SaveAs(savePath);
            UploadStatusLabel.Text = "The file was processed successfully.";
        }
        else
        {
            UploadStatusLabel.Text = "You did not specify a file to upload, or a file name, or the file was too large. Please try again.";
        }
    }

    protected void CheckButton_Click(object sender, EventArgs e)
    {
        if (FileName.Text.Length > 0)
        {
            string s = CheckForFileName() ? "exists already." : "does not exist.";
            UploadStatusLabel.Text = "The file name choosen " + s;
        }
        else
        {
            UploadStatusLabel.Text = "Specify a file name to check.";
        }
    }
    private Boolean CheckForFileName()
    {
        System.IO.FileInfo fi = new System.IO.FileInfo(Request.PhysicalApplicationPath + 
            saveDir + Server.HtmlEncode(FileName.Text));
            return fi.Exists;
    }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>PostBackTrigger Example</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:ScriptManager ID="ScriptManager1" runat="server" />
    The upload button is defined as a PostBackTrigger.<br/>
    <asp:UpdatePanel ID="UpdatePanel1" UpdateMode="Conditional" runat="server">
    <ContentTemplate>
    <fieldset>
    <legend>FileUpload in an UpdatePanel</legend>
       First, enter a file name to upload your file to: 
       <asp:TextBox ID="FileName" runat="server" />
       <asp:Button ID="CheckButton" Text="Check" runat="server" OnClick="CheckButton_Click" />
       <br />
       Then, browse and find the file to upload:
       <asp:FileUpload id="FileUpload1"                 
           runat="server">
       </asp:FileUpload>
       <br />
       <asp:Button id="UploadButton" 
           Text="Upload file"
           OnClick="UploadButton_Click"
           runat="server">
       </asp:Button>    
       <br />
       <asp:Label id="UploadStatusLabel"
           runat="server" style="color:red;">
       </asp:Label>           
    </fieldset>
    </ContentTemplate>
    <Triggers>
    <asp:PostBackTrigger ControlID="UploadButton" />
    </Triggers>
    </asp:UpdatePanel>
    </div>
    </form>
</body>
</html>

<%@ Page Language="VB" %>

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

<script runat="server">

    Private saveDir As String = "Uploads\\"

    Protected Sub UploadButton_Click(ByVal sender As Object, ByVal e As EventArgs)
        
        If (FileUpload1.HasFile AndAlso FileUpload1.FileBytes.Length < 10000 AndAlso _
           Not (CheckForFileName())) Then
            Dim savePath As String = Request.PhysicalApplicationPath & saveDir & _
               Server.HtmlEncode(FileName.Text)
            'Remove comment from the next line to upload file.
            'FileUpload1.SaveAs(savePath)
            UploadStatusLabel.Text = "The file was processed successfully."
        Else
            UploadStatusLabel.Text = "You did not specify a file to upload, or a file name, or the file was too large. Please try again."
        End If
        
    End Sub

    Protected Sub CheckButton_Click(ByVal sender As Object, ByVal e As EventArgs)
        If (FileName.Text.Length > 0) Then
            Dim s As String
            If (CheckForFileName()) Then
                s = "exists already."
            Else
                s = "does not exist."
            End If
            UploadStatusLabel.Text = "The file name choosen " & s
        Else
            UploadStatusLabel.Text = "Specify a file name to check."
        End If
    End Sub

    Private Function CheckForFileName() As Boolean
        Dim fi As New System.IO.FileInfo(Request.PhysicalApplicationPath & _
           saveDir & Server.HtmlEncode(FileName.Text))
        Return fi.Exists
    End Function

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>PostBackTrigger Example</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:ScriptManager ID="ScriptManager1" runat="server" />
    The upload button is defined as a PostBackTrigger.<br/>
    <asp:UpdatePanel ID="UpdatePanel1" UpdateMode="Conditional" runat="server">
    <ContentTemplate>
    <fieldset>
    <legend>FileUpload in an UpdatePanel</legend>
       First, enter a file name to upload your file to: 
       <asp:TextBox ID="FileName" runat="server" />
       <asp:Button ID="CheckButton" Text="Check" runat="server" OnClick="CheckButton_Click" />
       <br />
       Then, browse and find the file to upload:
       <asp:FileUpload id="FileUpload1"                 
           runat="server">
       </asp:FileUpload>
       <br />
       <asp:Button id="UploadButton" 
           Text="Upload file"
           OnClick="UploadButton_Click"
           runat="server">
       </asp:Button>    
       <br />
       <asp:Label id="UploadStatusLabel"
           runat="server" style="color:red;">
       </asp:Label>           
    </fieldset>
    </ContentTemplate>
    <Triggers>
    <asp:PostBackTrigger ControlID="UploadButton" />
    </Triggers>
    </asp:UpdatePanel>
    </div>
    </form>
</body>
</html>

注解

使用 PostBackTrigger 控件启用控件， UpdatePanel 以导致回发，而不是执行异步回发。

RegisterPostBackControl使用控件的方法ScriptManager以编程方式注册回发控件。 然后，当触发器控件执行回发时，可以调用 Update 控件的方法 UpdatePanel 。

备注

不支持以编程方式添加 PostBackTrigger 控件。

如果控件同时设置为PostBackTriggerAsyncPostBackTrigger控件，则会引发异常。

构造函数

PostBackTrigger()

初始化 PostBackTrigger 类的新实例。

属性

ControlID

获取或设置一个控件的名称，该控件充当 UpdatePanel 控件的 PostBackTrigger 控件。
Owner

获取对 UpdatePanel 所面向的 UpdatePanelTrigger 控件的引用。

(继承自 UpdatePanelTrigger)

方法

Equals(Object)

确定指定对象是否等于当前对象。

(继承自 Object)
FindTargetControl(Boolean)

搜索在 ControlID 属性中指定的控件。

(继承自 UpdatePanelControlTrigger)
GetHashCode()

作为默认哈希函数。

(继承自 Object)
GetType()

获取当前实例的 Type。

(继承自 Object)
HasTriggered()

返回一个指示是否已激活触发器的值。
Initialize()

初始化 PostBackTrigger 对象。
MemberwiseClone()

创建当前 Object 的浅表副本。

(继承自 Object)
ToString()

返回表示当前 PostBackTrigger 对象的字符串。

适用于

另请参阅