Serial port C# wpf received data continuous

Question

've made a GUI in WPF to read data via RS232 and.The only problem is I have to keep pressing a button to send a 'Receive data' command to my controller via RS232 so it sends the data back. I want to implement  this in continuously/real time so I don't have to keep pressing a button to communicate with my device. I've  written while loops and that just freezes my program, i've  also tried a checkbox so if it's checked it gets data and that also freezes the GUI.using backGroundWorker i want to do or Threads, below is my code please, TextBox1 is Receiving Data,TextBox2 is Sending data, am binding Receiving data to textbox1 string"Message", see code as attachemnt
thanks