System.IO.Exception error: “The requested operation cannot be performed on a file with a user-mapped section open.”

Question

I received a very weird IOException when writing to an XML file:

System.IO.IOException: The requested operation cannot be performed on a file with a user-map         


        

Answer 1

The OS or Framework can fail you, if you try to open the same file over and over again in a tight loop, for example

 while (true) {
   File.WriteAllLines(...)
 }

Of course, you don't want to actually do that. But a bug in your code might cause that to happen. The crash is not due to your code, but a problem with Windows or the .NET Framework.

If you have to write lots of files very quickly, you could add a small delay with Thread.Sleep() which also seems to get the OS off your back.

 while (i++<100000000) {
   File.WriteAllLines(...)
   Thread.Sleep(1);
 }