Question

有人可以告诉我为什么这不起作用？如果我将测试函数放入后面的代码中就可以了。如果我把它放到测试类中，数据总是没有。

2 个答案:

答案 0 :(得分：1)

答案 1 :(得分：0)

Answer 1

您必须返回一些DataTable值！

更新：我添加SqlDependency.Start(connstring)但缺少此行，您应该看到错误。这表明测试不是什么

Public Class TestClass
Public Shared Function Test() As DataTable
    Test = DirectCast(HttpContext.Current.Cache("Test"), DataTable)
    If Test Is Nothing Then
        Dim sql As String = "SELECT * from categories"
        Dim constring As String = ConfigurationManager.ConnectionStrings("HalloweenConnectionString").ConnectionString
        Using conn As New SqlConnection(constring)
            Using cmd As New SqlCommand(sql, conn)
                Dim dep As New SqlCacheDependency(cmd)
                SqlDependency.Start(constring)
                Test = New DataTable
                conn.Open()
                Test.Load(cmd.ExecuteReader(CommandBehavior.CloseConnection))
                HttpContext.Current.Cache.Insert("Test", Test, dep, Cache.NoAbsoluteExpiration, TimeSpan.FromHours(24))
            End Using
        End Using
    End If
End Function

结束班

Answer 2

这就是我最终这样做的方式。我仍然不清楚为什么我必须通过sqlcachedepency。

Partial Class _Default
Inherits System.Web.UI.Page
Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load
    Dim dep As SqlCacheDependency = Nothing
    ASPxGridView1.DataSource = TestClass.Test(dep)
    ASPxGridView1.DataBind()
    ASPxLabel1.Text = Now
End Sub
End Class

Public Class TestClass
Public Shared Function Test(ByRef dep As SqlCacheDependency) As DataTable
    Test = DirectCast(HttpRuntime.Cache("Test"), DataTable)
    If Test Is Nothing Then
        Dim sql As String = "SELECT field1,field2,field3 FROM test "
        Using conn As New SqlConnection(Materials.Conn)
            Using cmd As New SqlCommand(sql, conn)
                dep = New SqlCacheDependency(cmd)
                Test = New DataTable
                conn.Open()
                Test.Load(cmd.ExecuteReader(CommandBehavior.CloseConnection))
                HttpRuntime.Cache.Insert("Test", Test, dep, Cache.NoAbsoluteExpiration, TimeSpan.FromHours(24))
            End Using
        End Using
    End If
End Function
End Class

在共享类中缓存数据

2 个答案: