Check if the file is Open

Question

Can anyone please tell me if there is a way to find if a file is already open or not?

Answer 1

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

     try
     {
         stream = file.Open(FileMode.Open, FileAccess.ReadWrite, 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();
     }
     return false; 
}

Answer 2

As @pranay_stacker, but we need to make sure we close our file handle:

public bool IsFileInUse(string path)
{
  if (string.IsNullOrEmpty(path))
    throw new ArgumentException("'path' cannot be null or empty.", "path");

  try {
    using (var stream = new FileStream(path, FileMode.Open, FileAccess.Read)) { }
  } catch (IOException) {
    return true;
  }

  return false;
}

Answer 3

If you mean that you want to check if a file is open before you try to open it, then no. (At least not without going low level and examine every file handle that is open in the system.)

Besides, the information would be old when you get it. Even if the test would return that the file is not open, it could have been opened before you have a chance to use the return value.

So, the proper way to handle the situation is to try to open the file, and handle any error than may occur.

Answer 4

Agreed. I would create a designated class which wraps the open file logic or at least the test (IsFileAvailable). This will allow you to place the exception management with a class specifically responsible and make it reusable. You may even apply further logic, such as testing the file size to see if the file is being written to etc, to give a more detailed response. It will also make your consuming code much cleaner.