how to use AT-Command in C#

Question

I tried to send commands to a GSM modem or phone with C# using this code but it`s not working! Can anybody tell me what should I do ?

SerialPort sp = new SerialPort();
sp.PortName = "COM42";
sp.Open();
sp.Write("ATD09364191752");

Answer 1

1. You are not writing a newline after the ATD command. (I think you have to.)
2. You don't call sp.Flush(), so the command may be getting stuck in a buffer. Try adding this call after the Write() call.

Answer 2

You are relying on all default settings for baud-rate, handshake protocols etc. You may want to check the modem docs about those.