如何读取当前正在使用的文件，就像 Windows 复制文件时那样？

发布于 2024-10-06 00:39:19 字数 879 浏览 5 评论 0原文

我的应用程序之一旨在读取（并且仅读取）可能正在使用的文件。

但是，当读取已在 Microsoft Word 等中打开的文件时，此应用程序会抛出 System.IO.IOException：

进程无法访问文件“<文件名>”因为它正在被另一个进程使用。

用于读取该文件的代码是：

using (Stream stream = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete))
{
    // Do stuff here.
}

当然，由于该文件已被使用，因此出现此异常是预料之中的。

现在，如果我要求操作系统将文件复制到新位置，然后读取它，它就会起作用：

string tempFileName = Path.GetTempFileName();
File.Copy(fileName, tempFileName, true);
//                                         ↓ We read the newly created file.
using (Stream stream = new FileStream(tempFileName, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete))
{
    // Do stuff here.
}

File.Copy 的魔力是什么，它允许读取已被使用的文件应用程序，特别是如何使用这个魔法来读取文件而不制作临时副本？

原文

One of my applications is intended to read (and only read) files which may be in use.

But, when reading a file which is already opened in, for example, Microsoft Word, this application throws a System.IO.IOException:

The process cannot access the file '<filename here>' because it is being used by another process.

The code used to read the file is:

using (Stream stream = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete))
{
    // Do stuff here.
}

Of course, since the file is already used, this exception is expected.

Now, if I ask the operating system to copy the file to a new location, then to read it, it works:

string tempFileName = Path.GetTempFileName();
File.Copy(fileName, tempFileName, true);
//                                         ↓ We read the newly created file.
using (Stream stream = new FileStream(tempFileName, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete))
{
    // Do stuff here.
}

What is the magic of File.Copy which allows to read the file already used by an application, and especially how to use this magic to read the file without making a temporary copy?

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