Keeping changes after WriteFile, why it doesn' happen

[Gilberto Gil]

I'm trying to Write to my flash memory,, I've read the firts 512 bytes, modified that array changing some bytes for others and then using WriteFile API function, wrote (or tried) again those 512 first bytes into my memory again.. this WriteFile API function return 1 , after that I use CloseHandle API function closing the handle I used to interact with the memory...but, when I see my memory using WinHex(hex editor) the bytes there are the same before my program tries to write. why is this if I am even closing the handle and after close it my buffer(array of bytes read from my memory) seems modified.
My code:
[code=c#]

SafeFileHandle ptrFile = CreateFile("\\\ \.\\u:", DesiredAccess.G ENERIC_READ | DesiredAccess.G ENERIC_WRITE, ShareMode.FILE_ SHARE_READ_AND_ WRITE, IntPtr.Zero, CreationDisposi tion.OPEN_EXIST ING, FlagsAndAttribu tes.FILE_ATTRIB UTE_NORMAL, IntPtr.Zero);
byte[] buffer = new byte[512];
uint cantleidos = 0;

try
{
bool retor = SetFilePointerE x(ptrFile, 5, IntPtr.Zero, MoveMethod.FILE _BEGIN);
bool b = ReadFile(ptrFil e, buffer,512 , out cantleidos, IntPtr.Zero);
}
catch (Exception)
{
throw new Win32Exception( Marshal.GetLast Win32Error());
}

Buffer.BlockCop y(System.Text.E ncoding.UTF8.Ge tBytes("SOMETEX T".ToCharArray( )), 0, buffer,3,"SOMET EXT".ToCharArra y().Length);

uint wrote = 0;
bool c = WriteFile(ptrFi le, buffer, (uint)buffer.Le ngth, ref wrote, IntPtr.Zero);
int closed = CloseHandle(ptr File);
[/code]

[Plater]

You probably need to do some sort of FLUSH mechanism?

[Christian Binder]

Is the content of wrote-variable after line 19 correct? (should be 512, the same as buffer.Length)

you could print the buffer using string.Join("," , buffer), comparing it with the results in your hex-editor (maybe the file's bytes are already changed ... just a thought)

you could also try to use a file on your local hard drive to see if their is a difference.

[Plater]

wrote is passed by reference, meaning the function is changing it. It would be worthwhile to check the results of that value and value of c