Neeeed help with sequence diagram creating using C# code!

create a sequence diagram for the execute statement of the GoCommand class

public class GoCommand extends Command {
private GameCharacter thePlayer;
public GoCommand(GameCharacter theCharacter) {
this.thePlayer = theCharacter;
public String execute(String params) {
if (params == null) return “Go Where?”;
Exit theExit = getExit(params);
if (theExit == null) return “No exit there!”;
if (!takeExit(theExit))
return “I can’t take that exit now… Maybe it’s locked.”;
Location currentLocale = thePlayer.getCurrentLocation();
return currentLocale.getDescription();

I am pretty much in a fked up situation, i dont have an idea how to draw a sequence diagram using C# code…if anyone can help me with that??? I would appreciate that…Thanks