我正在用c#写一个程序,需要反复访问1个图像文件。大多数时候它是有效的,但如果我的计算机运行得很快,它会在文件保存回文件系统之前尝试访问该文件,并抛出一个错误:
文件正在被另一个进程使用
我想找到一个解决这个问题的方法,但我在谷歌上的所有搜索都只能通过使用异常处理来创建检查。这违背了我的宗教信仰,所以我想知道有没有更好的方法?
我正在用c#写一个程序,需要反复访问1个图像文件。大多数时候它是有效的,但如果我的计算机运行得很快,它会在文件保存回文件系统之前尝试访问该文件,并抛出一个错误:
文件正在被另一个进程使用
我想找到一个解决这个问题的方法,但我在谷歌上的所有搜索都只能通过使用异常处理来创建检查。这违背了我的宗教信仰,所以我想知道有没有更好的方法?
当前回答
我所知道的唯一方法是使用Win32独占锁API,这不是太快,但例子存在。
对于大多数人来说,一个简单的解决方案就是尝试/捕捉/睡眠循环。
其他回答
尝试将文件移动/复制到临时目录。如果可以的话,它没有锁,您可以安全地在临时目录中工作而不需要锁。否则就在x秒内再移动一次。
除了工作3-liner,只是为了参考:如果你想要完整的信息-在微软开发中心有一个小项目:
https://code.msdn.microsoft.com/windowsapps/How-to-know-the-process-704839f4
现发现于: https://github.com/TacticalHorse/LockFinder/blob/master/LockFinder.cs
引言:
The C# sample code developed in .NET Framework 4.0 would help in finding out which is the process that is having a lock on a file. RmStartSession function which is included in rstrtmgr.dll has been used to create a restart manager session and according to the return result a new instance of Win32Exception object is created. After registering the resources to a Restart Manager session via RmRegisterRescources function, RmGetList function is invoked to check what are the applications are using a particular file by enumerating the RM_PROCESS_INFO array.
它通过连接到“重启管理器会话”来工作。
重启管理器使用向会话注册的资源列表 确定哪些应用程序和服务必须关闭并重新启动。 资源可以通过文件名、服务短名称或 描述正在运行的应用程序的RM_UNIQUE_PROCESS结构。
为了满足你的特殊需求,它可能有点过度设计了…… 但如果这是你想要的,那就去拿vs-project吧。
I once needed to upload PDFs to an online backup archive. But the backup would fail if the user had the file open in another program (such as PDF reader). In my haste, I attempted a few of the top answers in this thread but could not get them to work. What did work for me was trying to move the PDF file to its own directory. I found that this would fail if the file was open in another program, and if the move were successful there would be no restore-operation required as there would be if it were moved to a separate directory. I want to post my basic solution in case it may be useful for others' specific use cases.
string str_path_and_name = str_path + '\\' + str_filename;
FileInfo fInfo = new FileInfo(str_path_and_name);
bool open_elsewhere = false;
try
{
fInfo.MoveTo(str_path_and_name);
}
catch (Exception ex)
{
open_elsewhere = true;
}
if (open_elsewhere)
{
//handle case
}
retry_possibility:
//somecode here
try
{
using(FileStream stream = file.Open(FileMode.Open, FileAccess.Read, FileShare.None))
{
stream.Close();
}
//write or open your file here
}
catch (IOException)
{
DialogResult dialogResult = MessageBox.Show("This file is opened by you or another user. Please close it and press retry.\n"+ expFilePath, "File Locked", MessageBoxButtons.RetryCancel);
if (dialogResult == DialogResult.Retry)
{
goto retry_possibility;
}
else if (dialogResult == DialogResult.Cancel)
{
//do nothing
}
}
您可以返回一个任务,它会在流可用时立即提供给您。这是一个简化的解决方案,但却是一个很好的起点。是线程安全的。
private async Task<Stream> GetStreamAsync()
{
try
{
return new FileStream("sample.mp3", FileMode.Open, FileAccess.Write);
}
catch (IOException)
{
await Task.Delay(TimeSpan.FromSeconds(1));
return await GetStreamAsync();
}
}
你可以像往常一样使用这个流:
using (var stream = await FileStreamGetter.GetStreamAsync())
{
Console.WriteLine(stream.Length);
}