Serial Port Programming

Hi guys I am new to serial port programming in C#, and I am finding it very difficult. I will be very much thankful in getting any kind of help from u guys. So my problem is: I am not able to find out the way how to detect whether the unit connected to serial port stops sending data. Application should to collect all the data which is coming from the serial port. But i am not able to detect when it is sending data and when it stops. In the application i have written the following code : DateTime dateTimeVariable = DateTime.Parse("01/01/1900"); while (true) { if(dateTimeVariable!=DateTime.Parse("01/01/1900")) { if (DateTime.Now.Subtract(dateTimeVariable).TotalSeconds > 2.1) { serialPort.DataReceived -= serialPort_DataReceived; serialPort.ErrorReceived -= serialPort_ErrorReceived; dateTimeVariable = DateTime.Parse("01/01/1900"); break; } } } dateTimeVariable is actually updated by datarevieved handler. Althought it is working fine but here i have to wait for 2.1 sec everytime even though there is no data in the serial port. Please help me to get the better code.