SqlCacheDependency 類別
定義
重要
部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。
在儲存於 ASP.NET 應用程式之 Cache 物件中的項目，和特定 SQL Server 資料庫資料表或 SQL Server 2005 查詢結果之間建立關聯性。 此類別無法獲得繼承。
public ref class SqlCacheDependency sealed : System::Web::Caching::CacheDependencypublic sealed class SqlCacheDependency : System.Web.Caching.CacheDependencytype SqlCacheDependency = class
inherit CacheDependencyPublic NotInheritable Class SqlCacheDependency
Inherits CacheDependency- 繼承
範例
下列程式代碼範例會使用 SqlDataSource 和 GridView 控件來顯示資料庫數據表。 載入頁面時，頁面會嘗試建立 SqlCacheDependency 物件。
SqlCacheDependency建立物件之後，頁面會將專案加入至 Cache ，並相依SqlCacheDependency於 物件。 您應該使用類似此處所示的例外狀況處理。
<%@ Page Language="C#" Debug="true" %>
<%@ import Namespace="System.Data.SqlClient" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
// <snippet2>
public void Page_Load(object Src, EventArgs E)
{
// Declare the SqlCacheDependency instance, SqlDep.
SqlCacheDependency SqlDep = null;
// Check the Cache for the SqlSource key.
// If it isn't there, create it with a dependency
// on a SQL Server table using the SqlCacheDependency class.
if (Cache["SqlSource"] == null) {
// Because of possible exceptions thrown when this
// code runs, use Try...Catch...Finally syntax.
try {
// Instantiate SqlDep using the SqlCacheDependency constructor.
SqlDep = new SqlCacheDependency("Northwind", "Categories");
}
// Handle the DatabaseNotEnabledForNotificationException with
// a call to the SqlCacheDependencyAdmin.EnableNotifications method.
catch (DatabaseNotEnabledForNotificationException exDBDis) {
try {
SqlCacheDependencyAdmin.EnableNotifications("Northwind");
}
// If the database does not have permissions set for creating tables,
// the UnauthorizedAccessException is thrown. Handle it by redirecting
// to an error page.
catch (UnauthorizedAccessException exPerm) {
Response.Redirect(".\\ErrorPage.htm");
}
}
// Handle the TableNotEnabledForNotificationException with
// a call to the SqlCacheDependencyAdmin.EnableTableForNotifications method.
catch (TableNotEnabledForNotificationException exTabDis) {
try {
SqlCacheDependencyAdmin.EnableTableForNotifications("Northwind", "Categories");
}
// If a SqlException is thrown, redirect to an error page.
catch (SqlException exc) {
Response.Redirect(".\\ErrorPage.htm");
}
}
// If all the other code is successful, add MySource to the Cache
// with a dependency on SqlDep. If the Categories table changes,
// MySource will be removed from the Cache. Then generate a message
// that the data is newly created and added to the cache.
finally {
Cache.Insert("SqlSource", Source1, SqlDep);
CacheMsg.Text = "The data object was created explicitly.";
}
}
else {
CacheMsg.Text = "The data was retrieved from the Cache.";
}
}
// </snippet2>
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title>ASP.NET Example</title>
</head>
<body>
<form id="form1" runat="server">
<p>
</p>
<p>
<asp:SqlDataSource id="Source1" runat="server" SelectCommand="SELECT * FROM [Categories]" UpdateCommand="UPDATE [Categories] SET [CategoryName]=@CategoryName,[Description]=@Description,[Picture]=@Picture WHERE [CategoryID]=@CategoryID" ConnectionString="<%$ ConnectionStrings:Northwind %>"></asp:SqlDataSource>
<asp:GridView id="GridView1" runat="server" DataKeyNames="CategoryID" AllowSorting="True" AllowPaging="True" DataSourceID="Source1"></asp:GridView>
</p>
<p>
</p>
<p>
<asp:Label id="CacheMsg" runat="server" AssociatedControlID="GridView1"></asp:Label>
</p>
</form>
</body>
</html>
<%@ Page Language="VB" Debug="True" %>
<%@ import Namespace="System.Data.SqlClient" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
' <snippet2>
Sub Page_Load(Src As Object, E As EventArgs)
' Declare the SqlCacheDependency instance, SqlDep.
Dim SqlDep As SqlCacheDependency
' Check the Cache for the SqlSource key.
' If it isn't there, create it with a dependency
' on a SQL Server table using the SqlCacheDependency class.
If Cache("SqlSource") Is Nothing
' Because of possible exceptions thrown when this
' code runs, use Try...Catch...Finally syntax.
Try
' Instantiate SqlDep using the SqlCacheDependency constructor.
SqlDep = New SqlCacheDependency("Northwind", "Categories")
' Handle the DatabaseNotEnabledForNotificationException with
' a call to the SqlCacheDependencyAdmin.EnableNotifications method.
Catch exDBDis As DatabaseNotEnabledForNotificationException
Try
SqlCacheDependencyAdmin.EnableNotifications("Northwind")
' If the database does not have permissions set for creating tables,
' the UnauthorizedAccessException is thrown. Handle it by redirecting
' to an error page.
Catch exPerm As UnauthorizedAccessException
Response.Redirect(".\ErrorPage.htm")
End Try
' Handle the TableNotEnabledForNotificationException with
' a call to the SqlCacheDependencyAdmin.EnableTableForNotifications method.
Catch exTabDis As TableNotEnabledForNotificationException
Try
SqlCacheDependencyAdmin.EnableTableForNotifications( _
"Northwind", "Categories")
' If a SqlException is thrown, redirect to an error page.
Catch exc As SqlException
Response.Redirect(".\ErrorPage.htm")
End Try
' If all the other code is successful, add MySource to the Cache
' with a dependency on SqlDep. If the Categories table changes,
' MySource will be removed from the Cache. Then generate a message
' that the data is newly created and added to the cache.
Finally
Cache.Insert("SqlSource", Source1, SqlDep)
CacheMsg.Text = "The data object was created explicitly."
End Try
Else
CacheMsg.Text = "The data was retrieved from the Cache."
End If
End Sub
' </snippet2>
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>ASP.NET Example</title>
</head>
<body>
<form id="form1" runat="server">
<p>
</p>
<p>
<asp:SqlDataSource id="Source1" runat="server" SelectCommand="SELECT * FROM [Categories]" UpdateCommand="UPDATE [Categories] SET [CategoryName]=@CategoryName,[Description]=@Description,[Picture]=@Picture WHERE [CategoryID]=@CategoryID" ConnectionString="<%$ ConnectionStrings:Northwind %>"></asp:SqlDataSource>
<asp:GridView id="GridView1" runat="server" DataKeyNames="CategoryID" AllowSorting="True" AllowPaging="True" DataSourceID="Source1"></asp:GridView>
</p>
<p>
</p>
<p>
<asp:Label id="CacheMsg" runat="server" AssociatedControlID="GridView1"></asp:Label>
</p>
</form>
</body>
</html>
備註
在所有支援的 SQL Server 版本上， (Microsoft SQL Server 7.0、Microsoft SQL Server 2000 和 SQL Server 2005) SqlCacheDependency 類別會監視特定的 SQL Server 資料庫數據表。 當資料表變更時，會從 Cache中移除與資料表相關聯的專案，並將新版的專案新增至 Cache。
類別 SqlCacheDependency 也支援在使用 SQL Server 2005 資料庫時與 System.Data.SqlClient.SqlDependency 類別整合。 SQL Server 2005 的查詢通知機制會偵測導致 SQL 查詢結果失效的數據變更，並從 中移除與 SQL 查詢 System.Web.Caching.Cache相關聯的任何快取專案。
您可以使用 SqlCacheDependency 類別，在使用 SQL Server 2005 時，將專案新增至 Cache 相依於 SQL Server 資料庫數據表或 SQL 查詢的應用程式。 您也可以搭配 指示詞使用這個類別 @ OutputCache ，讓輸出快取的頁面或使用者控件相依於 SQL Server 資料庫數據表。 最後，您可以使用 SqlCacheDependency 類別搭配 @ OutputCache page指示詞，在使用SQL Server 2005時，讓輸出快取的頁面相依於 SQL 查詢的結果。 使用者控件的指示詞不支援使用 SQL Server 2005 的 @ OutputCache 查詢通知。
注意
若要讓這個類別在使用數據表型通知時正確運作，資料庫和您想要建立相依性的任何數據表都必須啟用通知。 您可以呼叫 類別的方法 SqlCacheDependencyAdmin 或使用 aspnet_regsql.exe 命令列工具來啟用通知。 此外，應用程式 Web.config 檔案中必須包含適當的組態設定。
SqlCacheDependency搭配 SQL Server 2005 查詢通知使用 物件不需要任何明確的設定。 如需有關使用查詢通知時允許之 Transact-SQL 查詢類型限制的資訊，請參閱 SQL Server 檔。
下列範例顯示 ASP.NET Web.config档案，可啟用 SQL Server 資料庫數據表上的數據表型相依性。
<configuration>
<connectionStrings>
<add name="Northwind" connectionString="Data Source=(local); Initial Catalog=northwind; Integrated Security=true"; providerName="System.Data.SqlClient" />
</connectionStrings>
<system.web>
<caching>
<sqlCacheDependency enabled = "true" pollTime = "60000" >
<databases>
<add name="northwind"
connectionStringName="Northwind"
pollTime="9000000"
/>
</databases>
</sqlCacheDependency>
</caching>
</system.web>
</configuration>
建構函式
| SqlCacheDependency(SqlCommand) |
使用所提供的 SqlCacheDependency 建立快取索引鍵相依性，初始化 SqlCommand 類別的新執行個體。 |
| SqlCacheDependency(String, String) |
使用所提供的參數建立快取索引鍵相依性，初始化 SqlCacheDependency 類別的新執行個體。 |
屬性
| HasChanged |
取得值，指出 CacheDependency 是否已經變更。 (繼承來源 CacheDependency) |
| UtcLastModified |
取得上次變更相依性的時間。 (繼承來源 CacheDependency) |
