I'm using FileStream to write to a file, and watching the underlying system calls using Process Monitor. I'm having trouble with some file locking issues in a production deployment, so I'm looking at the details closely.
This sample code:
using (FileStream fs = new FileStream("c:\\temp\\test.txt", FileMode.Create, FileAccess.Write, FileShare.Read))
{
fs.Write(new byte[] { 1, 2, 3, 4, 5 }, 0, 5);
fs.Close();
}
Causes the following systems calls:
9:27:09.4561092 AM ConsoleApplication1.vshost.exe 2320 CreateFile C:\temp\test.txt SUCCESS Desired Access: Generic Read/Write, Disposition: OverwriteIf, Options: Synchronous IO Non-Alert, Non-Directory File, Open No Recall, Attributes: n/a, ShareMode: Read, AllocationSize: 0, OpenResult: Overwritten
9:27:12.2217409 AM ConsoleApplication1.vshost.exe 2320 WriteFile C:\temp\test.txt SUCCESS Offset: 0, Length: 5
9:27:12.2219901 AM ConsoleApplication1.vshost.exe 2320 CloseFile C:\temp\test.txt SUCCESS
9:27:12.2234484 AM ConsoleApplication1.vshost.exe 2320 CreateFile C:\temp\test.txt SUCCESS Desired Access: Generic Read, Write Attributes, Disposition: Open, Options: Synchronous IO Non-Alert, Non-Directory File, Complete If Oplocked, Random Access, Attributes: N, ShareMode: Read, Write, Delete, AllocationSize: n/a, OpenResult: Opened
9:27:12.2248664 AM ConsoleApplication1.vshost.exe 2320 QueryBasicInformationFile C:\temp\test.txt SUCCESS CreationTime: 10/29/2008 9:04:14 AM, LastAccessTime: 10/29/2008 9:27:12 AM, LastWriteTime: 10/29/2008 9:27:12 AM, ChangeTime: 10/29/2008 9:27:12 AM, FileAttributes: A
9:27:12.2250075 AM ConsoleApplication1.vshost.exe 2320 SetBasicInformationFile C:\temp\test.txt SUCCESS CreationTime: -1, LastAccessTime: -1, LastWriteTime: -1, ChangeTime: -1, FileAttributes: n/a
9:27:12.2255889 AM ConsoleApplication1.vshost.exe 2320 QueryStandardInformationFile C:\temp\test.txt SUCCESS AllocationSize: 8, EndOfFile: 5, NumberOfLinks: 1, DeletePending: False, Directory: False
9:27:12.2257571 AM ConsoleApplication1.vshost.exe 2320 ReadFile C:\temp\test.txt SUCCESS Offset: 0, Length: 5
9:27:12.2259825 AM ConsoleApplication1.vshost.exe 2320 ReadFile C:\temp\test.txt SUCCESS Offset: 0, Length: 5
9:27:12.2261588 AM ConsoleApplication1.vshost.exe 2320 ReadFile C:\temp\test.txt SUCCESS Offset: 0, Length: 5
9:27:12.2265161 AM ConsoleApplication1.vshost.exe 2320 ReadFile C:\temp\test.txt SUCCESS Offset: 0, Length: 2
9:27:12.2268237 AM ConsoleApplication1.vshost.exe 2320 ReadFile C:\temp\test.txt SUCCESS Offset: 0, Length: 5
9:27:12.2271332 AM ConsoleApplication1.vshost.exe 2320 ReadFile C:\temp\test.txt SUCCESS Offset: 0, Length: 5
9:27:12.2272841 AM ConsoleApplication1.vshost.exe 2320 ReadFile C:\temp\test.txt SUCCESS Offset: 0, Length: 5
9:27:12.2274779 AM ConsoleApplication1.vshost.exe 2320 ReadFile C:\temp\test.txt SUCCESS Offset: 0, Length: 5
9:27:12.2276249 AM ConsoleApplication1.vshost.exe 2320 ReadFile C:\temp\test.txt SUCCESS Offset: 0, Length: 5
9:27:12.2278766 AM ConsoleApplication1.vshost.exe 2320 ReadFile C:\temp\test.txt SUCCESS Offset: 0, Length: 5
9:27:12.2282577 AM ConsoleApplication1.vshost.exe 2320 ReadFile C:\temp\test.txt SUCCESS Offset: 0, Length: 5
9:27:12.2284476 AM ConsoleApplication1.vshost.exe 2320 QueryFileInternalInformationFile C:\temp\test.txt SUCCESS IndexNumber: 0x2d000000016b88
9:27:12.2286183 AM ConsoleApplication1.vshost.exe 2320 CloseFile C:\temp\test.txt SUCCESS
9:27:12.2288759 AM ConsoleApplication1.vshost.exe 2320 CreateFile C:\temp\test.txt SUCCESS Desired Access: Read Attributes, Write Attributes, Disposition: Open, Options: , Attributes: n/a, ShareMode: Read, Write, Delete, AllocationSize: n/a, OpenResult: Opened
9:27:12.2305722 AM ConsoleApplication1.vshost.exe 2320 QueryBasicInformationFile C:\temp\test.txt SUCCESS CreationTime: 10/29/2008 9:04:14 AM, LastAccessTime: 10/29/2008 9:27:12 AM, LastWriteTime: 10/29/2008 9:27:12 AM, ChangeTime: 10/29/2008 9:27:12 AM, FileAttributes: A
9:27:12.2307379 AM ConsoleApplication1.vshost.exe 2320 CloseFile C:\temp\test.txt SUCCESS
The first three IO calls are expected (create, write, close), but the the process goes on to read the file a dozen more times and repeatedly open and close it.
I've now observed this behavior on Win XP SP2, and Win 2003 x64. However, my Windows Vista machine at home behaves as expected (just the first three lines).
Any clues on why this is happening on non-Vista runtimes?