问题描述
我可以通过以下方法删除具有提供的路径的文件
I have the following method to delete a file with a provided path
private void DestroyFile(string path)
{
try
{
if (File.Exists(path))
{
File.Delete(path);
}
if (File.Exists(path))
{
throw new IOException(string.Format("Failed to delete file: '{0}'.", path));
}
}
catch (Exception ex)
{
throw ex;
}
}
如果文件存在于File.Delete方法之后，我将抛出IOException.具体地
I am getting the IOException that is thrown if the file exists after the File.Delete method. Specifically
我还确认执行完成后，该文件在path变量中的位置不存在.我想知道我是否在File.Delete之后更新文件系统与再次使用File.Exists对其进行检查之间的竞争条件下运行.有没有更好的方法可以顺利删除?我知道如果文件不存在，File.Delete不会返回错误，因此这些检查可能有点多余.我应该检查文件是否正在使用中，而不是根本不存在吗?
I have also confirmed that the file does not exist at the location in the path variable after the execution is complete. I am wondering if I am running up against a race condition between the file system updating after File.Delete and checking against it again with File.Exists. Is there a better way to smoothly delete? I know that File.Delete won't return an error if the file doesn't exist so maybe these checks are a bit redundant. Should I check if the file is in use rather than if it exists at all?
一些重要的附加信息:该程序可以并且确实可以成功运行，但是最近经常会看到此特定错误.
Some important additional information:The program can and does run successfully often but this particular error has been frequently seen recently.
推荐答案
File.Delete将标记文件以删除.实际上，只有在关闭所有句柄的情况下，文件才真正被删除(如果没有这样的句柄-在File.Delete返回之后，它将始终被删除).如针对 DeleteFile winapi函数(由C#File.Delete使用):
File.Delete will mark file for deletion. File really will be deleted only when all handles to it are closed (if there are no such handles - it will always be deleted after File.Delete returns). As documented for DeleteFile winapi function (which is used by C# File.Delete):
通常，没有删除文件的打开句柄.或者，如果有打开的句柄-它们通常没有删除"共享(此共享允许另一个进程将文件标记为删除)，所以当您尝试删除此类文件时-它要么被删除(没有打开的句柄)，要么拒绝访问或引发类似异常(某些句柄，但没有删除共享).
Usually there are no open handles to files you delete. Or, if there are open handles - they usually don't have "delete" share (this share allows another process to mark file for deletion), so when you try to delete such file - it either gets deleted (no open handles) or access denied or similar exception is thrown (some handles, but without delete share).
但是，有时某些软件(例如防病毒软件或搜索索引器)可能会打开具有删除"共享的任意文件，并将它们保留一段时间.如果您尝试删除此类文件-该文件将没有错误，并且在该软件关闭其句柄时实际上将删除该文件.但是，File.Exists对于此类待删除"文件将返回true.
However, sometimes some software, such as antivirus or search indexer, might open arbitrary files with "delete" share and hold them for some time. If you try to delete such file - it will go without errors and file really will be deleted when that software closes its handle. However, File.Exists will return true for such "pending delete" file.
您可以使用以下简单程序重现此问题:
You can reproduce this issue with this simple program:
public class Program {
public static void Main() {
string path = @"G:\tmp\so\tmp.file";
// create file with delete share and don't close handle
var file = new FileStream(path, FileMode.Create, FileAccess.ReadWrite, FileShare.Delete);
DestroyFile(path);
GC.KeepAlive(file);
}
private static void DestroyFile(string path) {
try {
if (File.Exists(path)) {
// no error
File.Delete(path);
}
// but still exists
if (File.Exists(path)) {
throw new IOException(string.Format("Failed to delete file: '{0}'.", path));
}
}
catch (Exception ex) {
throw ex;
}
}
}
您可以在上面的程序中再次尝试永久检查-该文件将一直存在，直到您关闭手柄为止.
You can retry File.Exists check forever in the program above - file will exist until you close the handle.
这就是您遇到的情况-某些程序使用FileShare.Delete对此文件打开了句柄.
So that's what happens in your case - some program has open handle to this file with FileShare.Delete.
您应该预料到这种情况.例如-只需删除File.Exists检查，因为您将文件标记为删除，并且该文件仍将被删除.
You should expect such situation. For example - just remove that File.Exists check, since you marked file for deletion and it will be deleted anyway.
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