HttpCachePolicy.SetValidUntilExpires(Boolean) 方法

  • 參考

定義

命名空間:
System.Web
組件:
System.Web.dll

指定 ASP.NET 快取是否應忽略使此快取無效之用戶端所傳送的 HTTP Cache-Control 標頭。

public:
 void SetValidUntilExpires(bool validUntilExpires);
public void SetValidUntilExpires (bool validUntilExpires);
member this.SetValidUntilExpires : bool -> unit
Public Sub SetValidUntilExpires (validUntilExpires As Boolean)

參數

validUntilExpires
Boolean

如果快取忽略 true 失效標頭，則為 Cache-Control，否則為 false。

範例

下列程式碼範例示範如何使用 SetValidUntilExpires 方法來指示用戶端傳送的任何快取無效標頭都會被忽略。

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>ASP.NET Example</title>
<script language="C#" runat="server">

// The following example demonstrates the SetValidUntilExpires method of the
// HttpCachePolicy class. The SetValidUntilExpires method is set to true so 
// that the ASP.NET cache ignores the HTTP Cache-Control headers and the page 
// remains in the cache until it expires.

void Page_Load(object Sender, EventArgs e)
{
   // Set the expiration time for the page.
   Response.Cache.SetExpires(DateTime.Now.AddSeconds(60));
   // Set the VaryByHeaders attribute with the value Accept-Language to true.
   Response.Cache.VaryByHeaders["Accept-Language"] = true;
   // ASP.NET ignores cache invalidation headers and the page remains in 
   // the cache until it expires.
   Response.Cache.SetValidUntilExpires(true);
   Response.Write("The SetValidUntilExpires method is set to true and ASP.NET cache should " + 
      "ignore the Cache-Control headers sent by the client that invalidate the cache.");
}

</script>
</head>
<body></body>
</html>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>ASP.NET Example</title>
<script language="VB" runat="server">

' The following example demonstrates the SetValidUntilExpires method of the
' HttpCachePolicy class. The SetValidUntilExpires method is set to true so that
' the ASP.NET cache ignores the HTTP Cache-Control headers and the page remains 
' in the cache until it expires.

Sub Page_Load(Sender As Object, e As EventArgs)
   ' Set the expiration time for the page.
   Response.Cache.SetExpires(DateTime.Now.AddSeconds(60))
   ' Set the VaryByHeaders attribute with the value Accept-Language to true.
   Response.Cache.VaryByHeaders("Accept-Language") = True
   ' ASP.NET ignores cache invalidation headers and the page remains in
   ' the cache until it expires.
   Response.Cache.SetValidUntilExpires(True)
   Response.Write("The SetValidUntilExpires method is set to true and the ASP.NET cache will " _
      & " ignore the Cache-Control headers sent by the client that invalidate the cache.")
End Sub 'Page_Load

</script>
</head>
<body></body>
</html>

備註

使用高階 <%@ OutputCache … %> 頁面指示詞時，方法 SetValidUntilExpires 會自動設定 true 為 。

提供此方法的原因是某些瀏覽器在重新整理頁面檢視時，將 HTTP 快取失效標頭傳送至網頁伺服器，並從快取收回頁面。 validUntilExpires當 參數為 true 時，ASP.NET 會忽略快取無效標頭，而且頁面會保留在快取中，直到過期為止。

SetValidUntilExpires.NET Framework 3.5 版引進。 如需詳細資訊，請參閱版本和相依性。

適用於