Question

我在IIS8.5上有一个自定义错误页面。有时，错误页面本身会抛出异常：

对象引用未设置为对象的实例。

这是我的代码背后的一部分：

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        HttpContext.Current.Response.StatusCode = 500
        'Dim CurrentException As Exception = Server.GetLastError()
        'virheettxt.text = CurrentException.Message
        Dim hostName = System.Net.Dns.GetHostName()



        Dim ctxOBJ As HttpContext
        Dim exceptionOBJ As Exception
        Dim errorInfoTXT As String

        ctxOBJ = HttpContext.Current()

        exceptionOBJ = ctxOBJ.Server.GetLastError()

        errorInfoTXT = " <br>Offending URL: " & iif(Not ctxOBJ Is Nothing, ctxOBJ.Request.Url.ToString(), "ei saatavilla") &
"<br>Source: " & iif(Not exceptionOBJ Is Nothing, exceptionOBJ.Source.ToString(), "ei saatavilla") &
"<br>Message: " & iif(Not exceptionOBJ Is Nothing, exceptionOBJ.Message.ToString(), "ei saatavilla") &
"<br>Stack trace: " & iif(Not exceptionOBJ Is Nothing, exceptionOBJ.StackTrace.ToString(), "ei saatavilla") &
"<br>Target Site: " & iif(Not exceptionOBJ Is Nothing, exceptionOBJ.TargetSite.ToString(), "ei saatavilla") &
"<br>Server: " & hostName
        Dim virheurlsc = ctxOBJ.Request.Url.ToString()



        ctxOBJ.Server.ClearError()

错误来自行：errorInfoTXT =“
违规网址：......

如果有办法捕获错误行，我在某些情况下也真的需要它......？

Answer 1

问题来自于使用Iif，它评估了真假案例。改为使用If() operator可以防止这种情况发生。

在尝试使用它之前，您还应该检查ctxOBJ是否为空，如果您在If（）中反转true和false参数，它将使它更简单：

Dim ctxOBJ As HttpContext = HttpContext.Current()
Dim exceptionOBJ As Exception = Nothing

If ctxOBJ IsNot Nothing Then
    exceptionOBJ = ctxOBJ.Server.GetLastError()
End If

Dim errorInfoTXT As String = " <br>Offending URL: " & If(ctxOBJ Is Nothing, "ei saatavilla", ctxOBJ.Request.Url.ToString()) &
"<br>Source: " & If(exceptionOBJ Is Nothing, "ei saatavilla", exceptionOBJ.Source.ToString()) &
"<br>Message: " & If(exceptionOBJ Is Nothing, "ei saatavilla", exceptionOBJ.Message.ToString()) &
"<br>Stack trace: " & If(exceptionOBJ Is Nothing, "ei saatavilla", exceptionOBJ.StackTrace.ToString()) &
"<br>Target Site: " & If(exceptionOBJ Is Nothing, "ei saatavilla", exceptionOBJ.TargetSite.ToString()) &
"<br>Server: " & hostName

asp.net自定义错误页面不起作用

1 个答案: