Question

I have deployed ASP.NET web site and ASP.NET web service on the same web server. Both of them require access to shared file.

How to implement/share lock that supports single writers and multiple readers? If somebody reads, nobody can write, but all still can read. If somebody writes, nobody can read/write.

Answer 1

to open file for writing with allowing other threads to read it use System.IO.File.Open method with System.IO.FileShare.Read. Ie.:

System.IO.File.Open('path.txt',System.IO.FileMode.OpenOrCreate,System.IO.FileAccess.ReadWrite,System.IO.FileShare.Read) 

Other (reading) threads should use System.IO.FileAccess.Read

Signature of Open method:

public static FileStream Open(string path, FileMode mode, FileAccess access, FileShare share); 

UPDATE If you need all instances to ocasionally write to file. Use Mutex class to reserve file writing. Ie.:

    Mutex mut = new Mutex('filename as mutex name');     mut.WaitOne();     //open file for write,      //write to file     //close file     mut.ReleaseMutex(); 

Hope it helps.