如何在删除该文件之前检查文件是否正在使用中。 [英] How to check if file is in use before deleting that file.

问题描述

其实我想将文件从一个文件夹复制到另一个文件夹，但在复制文件之前我必须检查目标文件夹中是否存在相同的文件，如果它存在，我必须删除该文件，然后将新文件复制到目标文件夹。



但我在服务器中收到未经授权的异常。我的错误是因为

i正在删除文件时正在使用，但我不知道发生什么事情。



string filename =file1.txt;

string filename1 =file1Copy.txt ;

string filesource = Server.MapPath（〜/ Lucky /）+ filename;

string destinationFile = Server.MapPath（〜/ LuckyCopy /）+ filename1 ;

if（System.IO.File.Exists（destinationFile））

{



System.IO .File.SetAttributes（destinationFile，FileAttributes.Normal）;

System.IO.File.Delete（destinationFile）;



} $ / $


System.IO.File.Copy（filesource，destinationFile，true）;

System.IO.File.SetAttributes（destinationFile， FileAttributes.Normal）;



我的尝试：



i有试过像

Actually i want to copy file from one folder to another folder,but before copying file i have to check same file is exists in destination folder,if it exists first i have to delete that file and then copy new file to destination folder.

but i am getting unauthorized exception in server.i am thing this error is because of
i am deleting file when that is in use,but i donot know excatly whats happening.

string filename = "file1.txt";
string filename1 = "file1Copy.txt";
string filesource = Server.MapPath("~/Lucky/") + filename;
string destinationFile = Server.MapPath("~/LuckyCopy/") + filename1;
if (System.IO.File.Exists(destinationFile))
{

System.IO.File.SetAttributes(destinationFile, FileAttributes.Normal);
System.IO.File.Delete(destinationFile);

}

System.IO.File.Copy(filesource, destinationFile, true);
System.IO.File.SetAttributes(destinationFile, FileAttributes.Normal);

What I have tried:

i have tried like

string filename = "file1.txt";
            string filename1 = "file1Copy.txt";
            string filesource = Server.MapPath("~/Lucky/") + filename;
            string destinationFile = Server.MapPath("~/LuckyCopy/") + filename1;
if (System.IO.File.Exists(destinationFile))
    {

                System.IO.File.SetAttributes(destinationFile, FileAttributes.Normal);
                System.IO.File.Delete(destinationFile);

            }

            System.IO.File.Copy(filesource, destinationFile, true);
            System.IO.File.SetAttributes(destinationFile, FileAttributes.Normal);

推荐答案

protected virtual bool IsFileLocked(FileInfo file)
{
    FileStream stream = null;

    try
    {
        stream = file.Open(FileMode.Open, FileAccess.Read, FileShare.None);
    }
    catch (IOException)
    {
        //the file is unavailable because it is:
        //still being written to
        //or being processed by another thread
        //or does not exist (has already been processed)
        return true;
    }
    finally
    {
        if (stream != null)
            stream.Close();
    }

    //file is not locked
    return false;
}

使用FileAccess.ReadWrite检查对于只读文件将失败，因此已修改解决方案以检查FileAccess.Read。虽然此解决方案有效，因为如果文件上有写入或读取锁定，尝试使用FileAccess.Read将失败，但是，如果文件上没有写入或读取锁定，则此解决方案将无效，即已经使用FileShare.Read或FileShare.Write访问打开（用于读取或写入）。



原文：过去几年我使用过此代码，并且我没有遇到任何问题。



了解你对使用异常的犹豫，但你无法一直避免这些：

Checking with FileAccess.ReadWrite will fail for Read-Only files so the solution has been modified to check with FileAccess.Read. While this solution works because trying to check with FileAccess.Read will fail if the file has a Write or Read lock on it, however, this solution will not work if the file doesn't have a Write or Read lock on it, i.e. it has been opened (for reading or writing) with FileShare.Read or FileShare.Write access.

ORIGINAL: I've used this code for the past several years, and I haven't had any issues with it.

Understand your hesitation about using exceptions, but you can't avoid them all of the time:

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