P/Invoke call just stops

I'm trying to write data to a serial port via P/Invoke (explicitly not with the SerialPort-class). Here's what I have so far:

[DllImport("kernel32", SetLastError = true)]
static extern IntPtr CreateFile(string filename,       // file name
                                uint desiredAccess,    // read? write?
                                uint shareMode,        // sharing
                                uint attributes,       // SecurityAttributes pointer
                                uint creationDisposition,
                                uint flagsAndAttributes,
                                uint templateFile);

[DllImport("kernel32", SetLastError = true)]
static extern bool WriteFile(IntPtr hFile,               // handle to file
                             byte[] lpBuffer,            // data buffer
                             uint nBytesToWrite,         // number of bytes to write
                             out uint nBytesWritten,     // number of bytes written
                             [In] ref NativeOverlapped overlapped); // overlapped buffer

const uint OPEN_EXISTING = 3;

_portHandle = CreateFile("COM1", GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, 0, 0);
uint bytesWritten;
var buffer = Encoding.ASCII.GetBytes("foo\r");
var overlapped = new NativeOverlapped();
WriteFile(_portHandle, buffer, (uint)buffer.Length, out bytesWritten, ref overlapped);

I get a _portHandle != -1 and can call WriteFile. But after the call, it does nothing. I can wait forever in VS-debug mode and wait for the call to return. Also, no exception is thrown.

Any kernel32开发者_如何学JAVA.dll-masters out there who can help me?

Thanks from Papa Mufflon for introducing that usable project, I derived that for myself and made very simple opensource project from it https://github.com/ebraminio/PInvokeSerialPort that you can also download it from https://nuget.org/packages/PInvokeSerialPort.

Of-course this project is not complete so any suggestion any feature requesting on it is valuable for me :)

Taken Serial Comm from John Hind (http://msdn.microsoft.com/en-us/magazine/cc301786.aspx) instead of developing my own :)

Works great!