/// <summary>Get/Create an instrument named 'sym'</summary>
public Instrument GetOrCreateInstrument(string sym)
{
// Don't request data for this instrument yet.
// The caller should add a reference to the instrument which will start the data flowing
var idx = Instruments.IndexOf(x => x.SymbolCode == sym);
var instr = idx >= 0 ? Instruments[idx] : Instruments.Add2(new Instrument(Model, sym));
return(instr);
}