Question

我在这里结束了我的智慧。我在以下代码行中不断收到NullReferenceException：

  ViewBag.PaypalError = "we were unable to retreive your cart.";

我知道就是那条线 - 我在文件的其他地方添加了一些代码，导致它获得一个新的行号，并且我的错误中的行号改为跟随它。我知道ViewBag不是null，因为我在它之前专门插入了if (ViewBag == null)测试。

为了使事情变得更奇怪，我有代码在执行进入导致上述声明的逻辑时发送电子邮件。该电子邮件永远不会被设置，但是之后发生的这行代码会引发异常，并且我从try / catch块中获取了捕获它的电子邮件。

我知道我应该避免使用ViewBag，并且我有一些想法可以重构代码而不需要它，但是没有一个能告诉我这个异常的来源。

有什么想法吗？试试试试？

编辑：这是代码的其余部分。这绝对不是我为之骄傲的代码，但它应该有效......

    public ActionResult PaypalConfirmation(string token, string payerID)
    {
        try
        {

            Cart cart = GetCurrentCart();
            if (cart == null)
            {
                                    // I never get this email.
                SendEmail("Paypal confirmation with null cart", "Token: " + token + ".<br><br>", requestData: Request);
                if (token != null && token != "")
                {
                    var tempCart = Cart.GetByAlternateOrderNumber(token);
                    if (tempCart != null)
                    {
                        cart = tempCart;
                    }
                    else
                    {
                        ViewBag.PaypalError = "we were unable to retreive your cart.";
                        return View("~/Views/Error/PayPal.cshtml");
                    }
                }
                else
                {
                    if (ViewBag == null)
                    {
                        SendEmail("VIEWBAG WAS NULL", "Token: " + token + ".<br><br>", requestData: Request);
                        return View("~/Views/Error/PayPal.cshtml");
                    }
                    else
                    {
                        // Line which errors
                        ViewBag.PaypalError = "we were unable to retreive your cart.";
                        return View("~/Views/Error/PayPal.cshtml");
                    }
                }
            }

            // More execution code here, including the "Everything worked" return.
        }
        catch (Exception ex)
        {
            try
            {
                var isNull = "";
                if (ViewBag == null) isNull = "ViewBag was null!<br><br>";
                SendEmail("Crash in Paypal Payment", isNull + ex.ToString(), requestData: Request);
                return View("~/Views/Error/PayPal.cshtml");
            }
            catch (Exception ex2)
            {
                SendEmail("Crash in reporting Paypal Crash!", ex.ToString() + "<br><br>---------------------<br><br>" + ex2.ToString());
                return View("~/Views/Error/PayPal.cshtml");
            }
        }
    }

来自catch区块的电子邮件：

System.NullReferenceException：未将对象引用设置为对象的实例。在C：############# \ Website \ Controllers \ CartController.cs：第137行的Website.Controllers.CartController.PaypalConfirmation（String token，String payerID）中

时间戳：3/6/2012 10:43:13上午   IP：#############
  请求的URL：/ Cart / PaypalConfirmation？token = EC-10L01937X56050826＆amp; PayerID = ############

用户代理：Mozilla / 5.0（Macintosh; Intel Mac OS X 10.6; rv：10.0.2）Gecko / 20100101 Firefox / 10.0.2

Answer 1

我怀疑这是来自ViewBag为空。添加或删除行时，它会更改其下方所有内容的行号。所以它可能是你改变之下的任何代码。如果新代码要求您向类添加新的using语句，则它可能已更改输出字节码中的每个行号。

您是否尝试过使用电子邮件作为日志记录的形式，而不仅仅是异常捕获？例如，当你尝试这个时会发生什么？不确定ex.Source属性是否有帮助？

public ActionResult PaypalConfirmation(string token, string payerID)
{
    var message = "Trying to confirm paypal.";
    SendEmail(message, message);

    try
    {
        message = "Getting current cart.";
        SendEmail(message, message);

        Cart cart = GetCurrentCart();

        message = cart == null
            ? "Current cart is null."
            : "Current cart is not null.";
        SendEmail(message, message);

        if (cart == null)
        {
            if (token != null && token != "")
            {
                message = "Getting temp cart by alternate order number.";
                SendEmail(message, message);

                var tempCart = Cart.GetByAlternateOrderNumber(token);

                message = "Getting temp cart by alternate order number.";
                SendEmail(message, message);

                if (tempCart != null)
                {
                    message = "Temp cart is not null";
                    SendEmail(message, message);

                    cart = tempCart;
                }
                else
                {
                    message = "Temp cart was null.";
                    SendEmail(message, message);

                    ViewBag.PaypalError = "we were unable to retreive your cart.";

                    message = "ViewBag.PayPalError set, returning view.";
                    SendEmail(message, message);

                    return View("~/Views/Error/PayPal.cshtml");
                }
            }
            else
            {
                message = "Setting ViewBag.PayPalError message.";
                SendEmail(message, message);

                // Line which errors
                ViewBag.PaypalError = "we were unable to retreive your cart.";

                message = "ViewBag.PayPalError set, returning view.";
                SendEmail(message, message);

                return View("~/Views/Error/PayPal.cshtml");
            }
        }

        // More execution code here, including the "Everything worked" return.
        message = "Executing more code.";
        SendEmail(message, message);
    }
    catch (Exception ex)
    {
        SendEmail(ex.GetType().Name + " caught", ex.Source);
        return View("~/Views/Error/PayPal.cshtml");
    }
}

ViewBag中* setting *值的NullReferenceException

1 个答案: