writing characters to com ports in c#

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C#

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Hey guys, was wondering if somebody could give me a hand...

I'm relativly new to c# and I'm having difficulty writing subsequent characters to a com port.
I basically need to send a user-input character followed by a short pause before the char 'x'.
I can send either the input character...OR a char defined in the program but only the first instruction is executed and I'm not sure why. I've tried a few methods but none seem to do the trick...

Here's snippets of my code, I'd really appriciate the help.

Ideally I'd like the program to wait for a char to be entered into buff[0]; send this character to com port; send 'x' char to com port and then wait for the next character to be entered into buff[0]

attempt one...

char[] buff = new char[1];
char[] xbuff = new char[1];

buff[0] = e.KeyChar;
xbuff[0] = 'x';

serialPort1.Write(buff, 0, 1);
System.Threading.Thread.Sleep(500);
serialPort1.Write(xbuff, 0, 1);
System.Array.Clear(buff, 0, 1);

attempt two...

string lettera = ((char)97).ToString();
string letterb = ((char)98).ToString();

serialPort1.Write(lettera);
System.Threading.Thread.Sleep(500);
serialPort1.Write(letterb);

For some reason on both attempts only the first char will be sent. I've been pulling my hair out for the last 2 days and would really be grateful for any ideas

M.