如何确定产生HResult的System.IO.IOException？ [英] How do I determine the HResult for a System.IO.IOException?

问题描述

该System.Exception.HResult财产受到保护。我怎么能偷看例外内，得到的HResult而不是诉诸反射或其它丑陋黑客？

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下面的情况：
我想写一个备份工具，打开和系统上读取文件。 我打开与FileAccess.Read和FileShare.ReadWrite文件，根据<一href="http://stackoverflow.com/questions/897796/how-do-i-open-an-already-opened-file-with-a-net-streamreader">this指导，因为我不关心，如果该文件是开放的，在写我读它的时候。

在某些情况下，当一个文件，我看是打开另一个应用程序时，System.IO.FileStream.Read（）方法抛出一个System.IO.IOException，该进程无法访问文件，因为另一个进程已锁定该文件的一个部。这是错误33 ，或者我认为HResult的0x80070021。 [修改：我相信，当另一个进程调用这个可以返回 LockFileEx 要在一个文件中锁定一个字节范围。]

我想停下来时，我得到这个错误重试。我认为这是采取适当的行动在这里。如果锁定过程中迅速释放字节范围锁，那么我就可以继续读取文件。<​​/ P>

我如何能分辨一个IOException因为这个原因，从其他人呢？我能想到的这些方式：

• 在私人反思 - 不想这样做。 PERF就会发臭。
• 在调用Exception.ToString（）和解析字符串。感觉哈克。将国际化的版本无法正常工作。

我不喜欢这些选项。是不是还有更好的，更清洁的方式？

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我只是搜查了一圈，发现<一href="http://msdn.microsoft.com/en-us/library/system.runtime.interopservices.marshal.gethrforexception.aspx">System.Runtime.InteropServices.Marshal.GetHRForException.会返回一个UINT像0x80070021？

解决方案

您可以使用Marshal.GetHRForException找回HRESULT：

  INT HR = Marshal.GetHRForException（前）;
 

参考

• <一个href="http://msdn.microsoft.com/en-us/library/system.runtime.interopservices.marshal.gethrforexception.aspx">http://msdn.microsoft.com/en-us/library/system.runtime.interopservices.marshal.gethrforexception.aspx

The System.Exception.HResult property is protected. How can I peek inside an exception and get the HResult without resorting to reflection or other ugly hacks?

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Here's the situation:
I want to write a backup tool, which opens and reads files on a system. I open the file with FileAccess.Read and FileShare.ReadWrite, according to this guidance, because I don't care if the file is open for writing at the time I read it.

In some cases, when a file I am reading is open by another app, the System.IO.FileStream.Read() method throws a System.IO.IOException, "The process cannot access the file because another process has locked a portion of the file". This is error 33, or I think HResult 0x80070021. [EDIT: I believe this can be returned when another process calls LockFileEx to lock a byte range within a file.]

I'd like to pause and retry when I get this error. I think this is the appropriate action to take here. If the locking process releases the byte-range lock quickly, then I can proceed reading the file.

How can I distinguish an IOException for this reason, from others? I can think of these ways:

• private reflection - don't wanna do that. Perf will stink.
• call Exception.ToString() and parse the string. Feels hacky. Won't work in i18n versions.

I don't like these options. Isn't there a better, cleaner way?

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I just searched around and found System.Runtime.InteropServices.Marshal.GetHRForException. Will that return a uint like 0x80070021?

解决方案

You can use Marshal.GetHRForException to get back the HResult:

int hr = Marshal.GetHRForException( ex );

Reference

• http://msdn.microsoft.com/en-us/library/system.runtime.interopservices.marshal.gethrforexception.aspx

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