C# Copy a File That is Being Written To

Question

I have read many other posts about this topic, but none appear to solve my problem directly (which surprises me).

Regardless...I wrote a log parser and very simply I am looking to copy a file from a remote machine locally, prior to parsing it. The file I am trying to copy is being written to constantly and I have ‘random’ success in copying it. Sometimes it will work and other times I will get an ‘access is denied’ or FileAccess error. A few other points:

• Whenever I use windows explorer to copy the file locally, I never
  have a problem copying it (which leads me to believe it’s perfectly
  possible to copy the file 100% of the time).
• I can always open the file using a text editor in its remove location.
• I do not own the file being written to and do not wish to ‘lock’ it in anyway such that the application that is actually writing to this file fails.

Does anyone have any suggestions for how to copy this file?

The current command I am using is:

File.Copy(this.txt_log_file_to_analyze.Text, sLogFileToAnalyze,true);

Answer 1

I guess you'll have to open the file using:

File.Open(this.txt_log_file_to_analyze.Text,FileMode.Open,FileAccess.Read,FileShare.ReadWrite)

and then copy the contents of the file 'manually' i.e.

using (var from = File.Open("path", FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
using (var to = File.OpenWrite("to_path"))
{
    from.CopyTo(to);
}

or if .NET 4.5 see How do I copy the contents of one stream to another?

Using the above api, you can specify that you do not want exclusive access to the file.