Question

在生产中偶尔会出现此错误，但我无法在DEV中重现它

System.NullReferenceException: Object reference not set to an instance of an object.     
at CommandCenterHeader.ascx.vb:line 23     
at System.EventHandler.Invoke(Object sender, EventArgs e)     
at System.Web.UI.Control.OnLoad(EventArgs e)     
at System.Web.UI.Control.LoadRecursive()     
at System.Web.UI.Control.LoadRecursive()     
at System.Web.UI.Control.LoadRecursive()     
at System.Web.UI.Control.LoadRecursive()     
at System.Web.UI.Control.LoadRecursive()     
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

CommandCenterHeader.ascx.vb：第23行是“Select Case Me.CurrentUser.UserType.ToLower”

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If Not IsPostBack Then
        Select Case Me.CurrentUser.UserType.ToLower
            Case "e", "f"
                lbtnccadmin.Visible = True
                lbtnccadmin.NavigateUrl = "/commandcenter/cc_admin.aspx"
            Case Else
                lbtnccadmin.Visible = False
        End Select
    End If
End Sub

<ComponentModel.Browsable(False)> _
    Protected ReadOnly Property CurrentUser() As CypStdLib.FL.QuotesDB.tblUserInfo
        Get
            If (Not IsNothing(Request.Cookies(cookieKey))) AndAlso (Not IsNothing(Request.Cookies(cookieKey)("userid"))) Then
                Dim uid As String = Request.Cookies(cookieKey)("userid") & ""
                If uid <> "" AndAlso IsNumeric(uid) Then
                    Dim curruser As New CypStdLib.FL.QuotesDB.tblUserInfo
                    If curruser.LoadByPrimaryKey(CLng(uid)) Then

                        Session("CurrentUser") = curruser
                        Return curruser
                    End If
                End If
            End If

            Return Nothing
        End Get
        'Set(ByVal value As CypStdLib.FL.QuotesDB.tblUserInfo)
        '    Current.Session("CurrentUser") = value
        'End Set
    End Property

Answer 1

显然层次结构Me.CurrentUser.UserType.ToLower中的对象一片空白。 Me或Me.CurrentUser或Me.CurrentUser.UserType

如果你不能想到为什么它可以为null或者什么可能是null ..我可以在切换案例之前添加一个log msg并将其存储在文件或数据库中并将此代码发送到生产测试目的（有时直到你弄清楚什么是错的）。这会让你知道出了什么问题

Answer 2

嗯，CurrentUser是否为空？如果没有，CurrentUser.UserType是否为空？

此外，ToLower需要作为方法调用... ToLower()

Answer 3

当用户会话在Web应用程序中超时时，是否会发生这种情况？

在select case语句上抛出NullReferenceException。有什么想法吗？

3 个答案: