File still open after File.AppendAllText

Question

I have a part of my code that writes to a text file. This is the only process active that is supposed to write to the file, and here is how it's done:

try
{
    File.AppendAllText(path, '\n' + tmp);
}
catch (Exception)
{
    lblError.Text = "Unable to save file";
}

This works fine like half of the time. But sometimes it throws an exception saying that the file is being used by another process. I looked up what process uses the file, and its w3wp.exe. I've read that File.AppendAllText closes the file once it's done with it, so it should be fine like I've done it. Right?

EDIT:

Description of purpose was requested, so here goes. This part of the code is supposed to append a line to a config textfile that another process will use. I am 100% certain that that process isn't currently running.

I might also add that this is an asp.net application (from code behind). So a user can write to config.txt from an asp-page.

I've tried this:

static readonly object saveLock = new object();
/*
 *  stuff
 */
protected void saveToConfig(string input)
{
    lock(saveLock)
    {
        File.AppendAllText(path, '\n' + input);
    }
}

But I still get the IOException-error saying that multiple processes are trying to access the file.

Answer 1

You could use Palmer to create some logic, which repeats the write if it fails:

Retry.On<IoException>().For(TimeSpan.FromSeconds(15)).With(context =>
    {
        File.AppendAllText(path, '\n' + tmp);
    });