3

我VirtualPathProvider用来从 SQL Server 表返回虚拟页面。这是工作 pk，我的VirtualPathProvider类文件中的代码如下。

我遇到的问题是，当我更改数据库中保存的虚拟页面数据（标题或页面文本）时，此更改不会显示在输出的页面上，因为原始页面已被缓存。

我已经阅读了一些关于将 GetCacheDependancy 添加到 VirtualPathProvider 类的文章，并且我尝试实现了几个示例，但原始页面仍然被缓存和显示。

我还尝试在虚拟页面 ( Response.AddCacheItemDependency("Pages")) 的页面加载中添加一些代码并编辑 global.asax：

Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
        ' Code that runs on application startup
        HttpContext.Current.Cache.Insert("Pages", DateTime.Now, Nothing, _
             System.DateTime.MaxValue, System.TimeSpan.Zero, _
             System.Web.Caching.CacheItemPriority.NotRemovable, _
             Nothing)

以防止缓存。但没什么用。

所以我要通过 VirtualPathProvider 类文件进行一些更改，以防止这些缓存问题。谢谢你尽你所能的帮助！

Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration
Imports System.Web
Imports System.Web.Security
Imports System.Web.UI
Imports System.Web.UI.HtmlControls
Imports System.Web.UI.WebControls
Imports System.Web.UI.WebControls.WebParts
Imports System.Web.Hosting
Imports System.Web.UI.MobileControls
Imports System.Collections.Generic

Public Class DbVirtualPathProvider
    Inherits VirtualPathProvider
    Public Shared Sub AppInitialize()
        Dim db As New DbVirtualPathProvider()
        HostingEnvironment.RegisterVirtualPathProvider(db)
    End Sub

Public Overrides Function FileExists(ByVal virtualPath As String) As Boolean
    Dim strConn As String = ConfigurationManager.ConnectionStrings("LIQUIDConnectionString").ConnectionString
    Dim cnn As New SqlConnection(strConn)
    cnn.Open()
    Dim cmd As New SqlCommand()
    cmd.Connection = cnn
    cmd.CommandText = "select count(*) from tbl_VirtualFiles where virtualpath='" & virtualPath & "'"
    Dim retval As Object = cmd.ExecuteScalar()
    cnn.Close()
    Dim i As Integer = Convert.ToInt32(retval)
    If i <= 0 Then
        'important as if no virtual file it looks for physical file
        Return Previous.FileExists(virtualPath)
    Else
        Return True
    End If
End Function

Public Overrides Function GetFile(ByVal virtualPath As String) As VirtualFile
    Dim file As New DbVirtualFile(virtualPath)
    If file.WebFormContent Is Nothing Then
        Return Previous.GetFile(virtualPath)
    Else
        Return file
    End If
End Function

End Class
4

1 回答 1

0

我认为您需要以与VirtualPathProvider.GetCacheDependency方法相同的方式覆盖虚拟路径提供程序的FileExists方法GetFile。所以它可以通过这种方式完成：

Public Overrides Function GetCacheDependency(virtualPath As String, virtualPathDependencies As IEnumerable, utcStart As DateTime) As CacheDependency
    If IsVirtualPathForDatabase(virtualPath) Then
        Return New CacheDependency(...)
    Else
        Return New Previous.GetCacheDependency(virtualPath, virtualPathDependencies, utcStart)
    End If
End Function

where is fakeIsVirtualPathForDatabase方法应该确定虚拟路径是否与您的数据库相关。如果是，您可以为此创建自己CacheDependency的（我为它留了一个位置...），否则您可以Previous.GetCacheDependency用于所有物理.aspx页面。

于 2011-04-08T12:49:46.940 回答