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Usage of the FileShare enumeration on Windows

 

Robbie Mosaic Fan

 

In Microsoft .NET class library, there is a FileShare enumeration. If you use
the FileStream constructor to create a FileStream object, you can use the
FileShare enumeration to specify share mode for the file. There are several
members: Delete, Inheritable, None, Read, ReadWrite and Write. In this article
I’m going to talk about three most basic members: Read, ReadWrite and Write.

 

The rule is simple: for a file to be shared between two processes, each process
should give the other enough FileShare rights.

 

Let’s use two processes as an example. Process A and Process B. If A opens a
file for reading, and B then opens the same file for writing, in which
situation will both operations succeed? Because A is reading, B must open the
file with at least FileShare.Read. It can also open the file with
FileShare.ReadWrite, which includes FileShare.Read. However, for process B to
succeed, it also requires A to open the file with at least FileShare.Write.

 

What if B opens the file with read and write, that is, FileAccess.ReadWrite?
Then following the rule discribed above, A must use FileShare.ReadWrite.

 

Just that simple.