Dataloader

What is the difference between the 2?

InstrumentDataRequest Req = new InstrumentDataRequest();
InstrumentDataRequest Req = Bars.Request;

When I use the Bars.Request the data I received is tied to the bars of the main chart.
This one downloads data one bar at a time from the being of the chart data.

Req.Range = DataRequest.CreateFromTo(Bars.Time[1], Bars.Time[0]);

This one times out with no data downloaded

Req.Range = DataRequest.CreateBarsBack(DateTime.Now, 50);

When I try to use new InstrumentDataRequest() and fill in the stock data, I get an error reading symbol not found.
If I wanted to download data using the underlying Instrument's Symbol but not the bar length, which one do I use?

Hello beggar,

InstrumentDataRequest Req = new InstrumentDataRequest(); - creates empty requests, and all the fields have to be filled manually.
InstrumentDataRequest Req = Bars.Request; - creates a copy of request from the base data series.