Problem with Serial Port and AutoResetEvent

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C#

Dear all

I have a communication class which does use SerialPort to communicate. My first implementation polled the port and was very efficient. Because I hate polling I tried to replace it.

My idea:
- I hook into SerialPort.DataReceived. DataReceived will be called from a the SerialPort thread
- My DataReceived checks the condition and set an AutoResetEvent to signaled if the condition meats the criterion
- The main thread waits using AutoResetEvent.WaitOne().

Problem:
Even while DataReceived signales AutoResetEvent, the main thread freezes.

Thanks in advance.
Regards


code fragments:

class CommunicationDeviceSerialPort : CommunicationDevice
{
  System.IO.Ports.SerialPort  serialPort  = new System.IO.Ports.SerialPort();
  AutoResetEvent              recSynchObj = new AutoResetEvent(false)
	
  // Hook for SerialPort.DataReceived. Called by the SerialPort receiver thread
  private void SerialDataReceivedEvent(object sender, SerialDataReceivedEventArgs e)
  {
    // Acoording to MSN docu, this will be called from a background thread


    // read in pending SerialPort data into deviceBuffer
    ... deviceBuffer

    // Check condition
    if (deviceBuffer meats my condition)
       recSynchObj.Set();
  }

  // Communicate will be called from the main thread 
  public int Communicate(String Command, int TimeoutMS, out Data)
  {
    // Some Cleanup
    ...

    // Send the command
    serialPort.Write(Command);

    // Ininite timeou for tests
    bool xSignaled= recSynchObj.WaitOne();  

    //************************************
    //****It never comes out of WaitOne one line above. Why???*****
    //************************************

    if (xSignaled)
    {
        // Read data from devicebuffer
        ...
    }

    // With Progress in final version
    /*
    while(true)
    {
      bool xSignaled= recSynchObj.WaitOne(250);
      if (xSignaled)
      {
        // Read data from devicebuffer
        ...
        break;
      }
      // ShowProgress();
      // CheckTimeout()
    }
    */
  }
}

class FormMain
{
  CommunicationDevice commDevice= new CommunicationDeviceSerialPort();

  private void DoCommunicate
  {
    // Send somthing
    commDevice.Communicate(cmd, 2000, );	
  }	
}