通过

HttpResponseSubstitutionCallback 委托

  • 参考

定义

命名空间:
System.Web
程序集:
System.Web.dll

表示处理缓存后替换的方法。

public delegate System::String ^ HttpResponseSubstitutionCallback(HttpContext ^ context);
public delegate string HttpResponseSubstitutionCallback(HttpContext context);
type HttpResponseSubstitutionCallback = delegate of HttpContext -> string
Public Delegate Function HttpResponseSubstitutionCallback(context As HttpContext) As String

参数

context
HttpContext

包含对页的 HTTP 请求信息的 HttpContext，该页带有需要缓存后替换的控件。

返回值

String

在发送到客户端之前插入到缓存的响应的内容。

示例

下面的代码示例演示如何以编程方式将控件添加到 Substitution 输出缓存网页。 加载页面时，当前日期和时间在标签中向用户显示。 页面的此部分每 60 秒缓存并更新一次。 Substitution控件执行时，它会调用 GetCurrentDateTime 方法，该方法必须与委托的HttpResponseSubstitutionCallback签名匹配。 方法返回 GetCurrentDateTime 的字符串将向用户显示。 页的此部分不会缓存，每次刷新页面时都会更新。 控件 MethodName 的 Substitution 属性获取或设置回调方法的名称。

<%@ outputcache duration="60" varybyparam="none" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server" language="C#">  
  
  void Page_Load(object sender, System.EventArgs e)
  {
    // Programmatically create a Substitution control.
    Substitution Substitution1 = new Substitution();
    
    // Specify the callback method.
    Substitution1.MethodName = "GetCurrentDateTime";
    
    // Add the Substitution control to the controls
    // collection of PlaceHolder1.
    PlaceHolder1.Controls.Add (Substitution1);        

    // Display the current date and time in the label.
    // Output caching applies to this section of the page.
    CachedDateLabel.Text = DateTime.Now.ToString();    
  }
  
  // The Substitution control calls this method to retrieve
  // the current date and time. This section of the page
  // is exempt from output caching. 
  public static string GetCurrentDateTime (HttpContext context)
  {
    return DateTime.Now.ToString ();
  }
  
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
  <title>Substitution Class Example</title>
</head>
<body>
  <form id="Form1" runat="server">
  
    <h3>Substitution Constructor Example</h3>  
    
    <p>This section of the page is not cached:</p>
    <asp:placeholder id="PlaceHolder1"
      runat="Server">
    </asp:placeholder>
    
    <br />
    
    <p>This section of the page is cached:</p>
    
    <asp:label id="CachedDateLabel"
      runat="Server">
    </asp:label>
    
    <br /><br />
    
    <asp:button id="RefreshButton"
      text="Refresh Page"
      runat="Server">
    </asp:button>     

  </form>
</body>
</html>

<%@ outputcache duration="60" varybyparam="none" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server" language="VB">  
  
  Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
    ' Programmatically create a Substitution control.
    Dim Substitution1 As New Substitution
    
    ' Specify the callback method.
    Substitution1.MethodName = "GetCurrentDateTime"
    
    ' Add the Substitution control to the controls
    ' collection of PlaceHolder1.
    PlaceHolder1.Controls.Add(Substitution1)
    
    ' Display the current date and time in the label.
    ' Output caching applies to this section of the page.
    CachedDateLabel.Text = DateTime.Now.ToString()
  End Sub
  
  ' The Substitution control calls this method to retrieve
  ' the current date and time. This section of the page
  ' is exempt from output caching. 
  Shared Function GetCurrentDateTime(ByVal context As HttpContext) As String
    Return DateTime.Now.ToString()
  End Function
  
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
  <title>Substitution Constructor Example</title>
</head>
<body>
  <form id="Form1" runat="server">
  
    <h3>Substitution Constructor Example</h3>  
    
    <p>This section of the page is not cached:</p>
    <asp:placeholder id="PlaceHolder1"
      runat="Server">
    </asp:placeholder>
    
    <br />
    
    <p>This section of the page is cached:</p>
    
    <asp:label id="CachedDateLabel"
      runat="Server">
    </asp:label>
    
    <br /><br />
    
    <asp:button id="RefreshButton"
      text="Refresh Page"
      runat="Server">
    </asp:button>     

  </form>
</body>
</html>

注解

委托HttpResponseSubstitutionCallback与 WriteSubstitution 方法结合使用，用于呈现 和 AdRotator 控件的Substitution后缓存内容。

Substitution对于 控件，使用 MethodName 属性指定要在控件执行时调用的Substitution回调方法的名称。 指定的回调方法必须是页面上或包含 Substitution 该控件的用户控件上的静态方法。 回调方法的签名必须与接受HttpContext参数并返回字符串的HttpResponseSubstitutionCallback委托的签名匹配。

AdRotator对于 控件，除非为 AdCreated 事件提供事件处理程序，否则呈现与页面缓存无关。 AdCreated如果没有事件处理程序，则使用后缓存替换来呈现AdRotator内容。

扩展方法

GetMethodInfo(Delegate)

获取指示指定委托表示的方法的对象。

适用于

另请参阅