如何解决这个问题，它显示空引用异常未得到处理

本文介绍了如何解决这个问题，它显示空引用异常未得到处理的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

void RSSClient_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e) { var RSSDATA = from rss in XElement.Parse(e.Result).Descendants("item") select new RSSItems{ Title = rss.Element("title").Value, publicationDate = rss.Element("pubDate").Value, Description = rss.Element("description.").Value, Link = rss.Element("link").Value, }; RSSList.ItemsSource = RSSDATA;

===编辑：请在代码标签中发布您的代码= == CodingK

=== Please post your code in code tags=== CodingK

推荐答案

我们不能说 - 因为我们不知道错误发生在哪一行，我们可以;单独运行该代码。 它可能是任何东西：Element集合可能不包含你要求它的一个字段，因为你拼写错误，或RSSList可能为null - 我们只是'知道。 所以用调试器看一下：在方法的第一行放一个断点，看一下它要处理的数据 - 如果你必须，并寻找空值或坏值。 但是我们不能为你做到这一点！ We can't say - because we have no idea what line the error coccurs on, and we can;t run that code in isolation. It could be anything: the Element collection might not contain one of the fields you ask it for because you spelled it wrong, or RSSList could be null - we just don't know. So look at it with the debugger: put a breakpoint on the first line in the method and look at the data it's going to process - step if you have to, and look for nulls, or bad values. But we can't do it for you!

你没有显示带有对象引用未设置为对象实例消息的异常位置。 不用担心。这是检测和修复的最简单的案例之一。它只是意味着某些引用类型的某个成员/变量通过使用和它的实例（非静态）成员解除引用，这要求此成员/变量为非null，但实际上它似乎为null。只需在调试器下执行它，它将停止抛出异常的执行。在该行上设置一个断点，重新启动应用程序并再次到达这一点。评估下一行中涉及的所有引用，并查看哪一个为null，而不需要为null。解决这个问题之后，修复代码：要么确保将成员/变量正确初始化为非空引用，要么将其检查为null，如果为null，则执行其他操作。 另请参阅：想要在按钮点击时显示下一条记录。但是如果下一条记录功能的条件对象引用没有设置为对象的实例 [ ^ ]。 有时候，你不能在调试器下，由于一个或另一个原因做到这一点。一个非常讨厌的情况是，只有在调试信息不​​可用时构建软件时才会出现问题。在这种情况下，你必须使用更难的方式。首先，你需要确保你永远不会通过静默处理异常来阻止异常的传播（这是开发人员对自己的犯罪，但很常见）。您需要在每个线程的最顶层堆栈帧上捕获绝对所有异常。如果处理类型 System.Exception 的异常，则可以执行此操作。在处理程序中，您需要记录所有异常信息，尤其是 System.Exception.StackTrace ： msdn.microsoft/en-us/library/system.exception.aspx [ ^ ]， msdn.microsoft/en-us/library/system.exception。 stacktrace.aspx [ ^ ]。 堆栈跟踪只是一个字符串，显示从throw语句到处理程序的异常传播的完整路径。通过阅读，您总能找到目的。对于日志记录，使用类 System.Diagnostics.EventLog ： msdn.microsoft/en-us/library/system.diagnostics.eventlog.aspx [ ^ ]。

-SA

You did not show where the exception with the message "Object reference not set to an instance of an object" is thrown. Not to worry. This is one of the very easiest cases to detect and fix. It simply means that some member/variable of some reference type is dereferenced by using and of its instance (non-static) members, which requires this member/variable to be non-null, but in fact it appears to be null. Simply execute it under debugger, it will stop the execution where the exception is thrown. Put a break point on that line, restart the application and come to this point again. Evaluate all references involved in next line and see which one is null while it needs to be not null. After you figure this out, fix the code: either make sure the member/variable is properly initialized to a non-null reference, or check it for null and, in case of null, do something else. Please see also: want to display next record on button click. but got an error in if condition of next record function "object reference not set to an instance of an object"[^]. Sometimes, you cannot do it under debugger, by one or another reason. One really nasty case is when the problem is only manifested if software is built when debug information is not available. In this case, you have to use the harder way. First, you need to make sure that you never block propagation of exceptions by handling them silently (this is a crime of developers against themselves, yet very usual). The you need to catch absolutely all exceptions on the very top stack frame of each thread. You can do it if you handle the exceptions of the type System.Exception. In the handler, you need to log all the exception information, especially the System.Exception.StackTrace: msdn.microsoft/en-us/library/system.exception.aspx[^], msdn.microsoft/en-us/library/system.exception.stacktrace.aspx[^]. The stack trace is just a string showing the full path of exception propagation from the throw statement to the handler. By reading it, you can always find ends. For logging, it's the best (in most cases) to use the class System.Diagnostics.EventLog: msdn.microsoft/en-us/library/system.diagnostics.eventlog.aspx[^]. Good luck,

—SA