CODEWITHSUNDEEP
c#.netasynchronousconcurrencytask
Ambidex
Ambidex

Reputation: 372

Issues with File Copy Asynchronously

I am copying files asynchronously with the article Microsoft provided https://learn.microsoft.com/en-us/dotnet/standard/io/asynchronous-file-i-o

The issue I am running into using this is that when the files are finished copying, it doesn't keep the date modified value and is set to the time the file was created.

To compensate for that, I am trying to set the date modified time for each file after their finished copying with the File.SetLastWriteTime static method.

foreach (var file in dir.EnumerateFiles())
{
    string temppath = Path.Combine(destDirName, file.Name);
    using (FileStream reader = new FileStream(file.FullName, FileMode.Open, FileAccess.Read))
    {
        using (FileStream writer = new FileStream(temppath, FileMode.Create, FileAccess.ReadWrite))
        {
            await reader.CopyToAsync(writer);
            File.SetLastWriteTime(temppath, file.LastWriteTime);
        }
    }
}

Unfortunately, it seems that the File.SetLastWriteTime method executes immediately before await reader.CopyToAsync(writer) has finished.

How can I make sure that the File.SetLastWriteTime method isn't executed until after reader.CopyToAsync has finished?

It appears to work as intended if I change the method to copy synchronously within a Task.Run, but not sure if that is the correct way to do it.

Upvotes: 1

Views: 2290

Answers (1)

Ambidex
Ambidex

Reputation: 372

I was able to figure it out.

The reason why it couldn't set the file time is because it was still within the stream.

I simply moved the method outside of the write stream and that resolved the problem.

       foreach (var file in dir.EnumerateFiles())
        {
            string temppath = Path.Combine(destDirName, file.Name);
            using (FileStream reader = new FileStream(file.FullName, FileMode.Open, FileAccess.Read))
            {
                using (FileStream writer = new FileStream(temppath, FileMode.Create, FileAccess.ReadWrite))
                {
                    await reader.CopyToAsync(writer);

                }
               File.SetLastWriteTime(temppath, file.LastWriteTime);
            }
        }

Upvotes: 2

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