I’m using a logging library which is writing to a local log file and I also have a diagnostic tool which allows me to view the log files, but if I try to use File.Open I get the IOException,

“the process cannot access the file because it is used by another process”

this is obviously self-explanatory (and sadly not the first time I’ve had this and had to try and recall the solution).

So to save me searching for it, here the solution which allows me to open a file that’s already opened for writing to by another process

using (var stream = 
   File.Open(currentLogFile, 
      FileMode.Open, 
      FileAccess.Read, 
      FileShare.ReadWrite))
{
   // stream reading code
}

The key to the File.Open line is the FileShare.ReadWrite. We’re interested in opening the file to read but we still need to specify the share flag(s) FileShare.ReadWrite.