Implementing virtual drive with Dokan. Stuck on WriteFile

Question

I'm writing my filesystem using C# and Dokan library and got stuck on WriteFile.

 public int WriteFile(
            String filename,
            Byte[] buffer,
            ref uint writtenBytes,
            long offset,
            DokanFileInfo info)
        {           
            try
            {
                FileStream fs = File.OpenWrite( GetFullPath(filename) , FileMode.Open );              
                fs.Seek(offset, SeekOrigin.Begin);
                fs.Lock(offset, buffer.Length);
                fs.Write(buffer, 0, buffer.Length);
                fs.Unlock(offset, buffer.Length);
                writtenBytes = (uint)buffer.Length;
                return 0;
            }
            catch (Exception e)
            {
                Console.WriteLine("FAIL WriteFile {0}", e.Message);
                return -1;
            }
        }

When I run app and open txt file from Dokan's virtual drive, add some line and try to save it. I get error from notepad "The parameter is incorect".

In code I get exception on File.OpenWrite() call. The exception is System.IO.IOException. Message: "The process cannot access the file foo.txt because it is being used by another process."

• File is opened only by notepad.
• Same behavior can be observed with Mirror example delivered with Dokan library
• I added admin permissions to my program in the manifest, it didn't help

Dokan is supposed to work as proxy, allowing to call WriteFile defined by user, right? How can I do this if it's locked for writing?

Please help. Maybe you have any experience with Dokan or any clue why it's not working.

I'm using - Win 7 Pro x64 - 64 bit Dokan driver - App is compiled as x86

Answer 1

You must call Dispose on stream before leaving the method. That's not the best solution. You shuld construct file stream in CreateFile , pass it to info.Context and the use it in ReadFile , WriteFile and call dispose on it in Cleanup.