VB.NET SqlCacheDependency构造函数代码示例

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