View source for 4.7.4 Receiving the data for any symbol and any resolution. DataLoader

The studies can download the data for any symbol that is available in the database even if a chart for this instrument is not created in MultiCharts .NET.  This service is available via the DataLoader property returned by the IDataLoader interface. This interface contains the methods for starting and stopping the data downloading process. 


To start the data downloading process it is necessary to call the following method: 
<syntaxhighlight lang="csharp">
IDataLoaderResult BeginLoadData(InstrumentDataRequest Request, LoadDataCallback Sink, object State)
</syntaxhighlight>
where '''{{color|blue|InstrumentDataRequest}}''' is the structure that determines the data request parameters. It contains the following fields:

* {{color|blue|public string Symbol}} – instrument name;

* {{color|blue|public string DataFeed}} – data feed name;

* {{color|blue|public string Exchange}} – exchange name;

* {{color|blue|public ESymbolCategory Category}} – symbol category (for example Future, Stock, Index, etc.);

* {{color|blue|public Resolution Resolution}} – request resolution 


Resolution structure helps to determine both regular  and irregular resolutions. 

* <div style="background-color: #E5F6FF;">'''Example of determining a regular resolution:'''</div>
<syntaxhighlight lang="csharp">
Resolution _res = new Resolution(EResolution.Tick, 10);
</syntaxhighlight>
If the request resolution is set in this way then 10-tick data will be requested. 


* <div style="background-color: #E5F6FF;">'''Example of determining an irregular resolution:'''</div>
<syntaxhighlight lang="csharp">
Resolution _res = Resolution.CreatePointAndFigure(EResolution.Tick, 10, 0.001, 3, PointAndFigureBasis.HighLow, true);
</syntaxhighlight>


If the request resolution is set in this way, then the PointAndFigure resolution based on a 10-tick resolution, BoxSize = 0.001, Reversal = 3, HighLow Basis and BreakOnSession enabled will be returned.


* {{color|blue|public DateTime From}} – the start date of requested data. This field is outdated and it is better to use the Range field.

* {{color|blue|public DateTime To}} – the end date of requested data. This field is outdated and it is better to use the Range field.

* {{color|blue|public DataRequest Range}} – the range of requested data

* {{color|blue|public RequestTimeZone TimeZone}} – the time zone that will be applied to the requested data. The available values are: Local, Exchange and GMT.  The Default value is Local.

* {{color|blue|public RequestQuoteField QuoteField}} – the quote field of the requested data. The available values are: Bid, Ask and Trade. The Default value isTrade.

* {{color|blue|public string SessionName}} – the name of the session that will be applied to the requested data. 

* {{color|blue|public bool FilterOutOfRangeData}} –this indicates if “odd” data should be cut off. Here the “odd” data is defined as the data before the request start time and the data after the request end time. 

* {{color|blue|public bool Subscribe2RT}} – this indicates whether the real time data subscription is required or if only historical data is needed.


'''{{color|blue|LoadDataCallback}}''' – is a delegate with the following signature:
<syntaxhighlight lang="csharp">
public delegate void LoadDataCallback(IDataLoaderResult Result); 
</syntaxhighlight>

It is used to call back the data request results. This function is called in a separate thread, different from one where {{color|blue|BeginLoadData}} is called.


:'''{{color|blue|IDataLoaderResult}}''' –  the interface that provides information in the data request results. It contains the following fields:
* {{color|blue|bool IsCompleted { get; }}} – indicates whether the data downloading process is complete or not. 

* {{color|blue|object State { get; }}} – returns the current state that was set in BeginLoadData method.

* {{color|blue|Bar[] Data { get; }}} – returns the downloaded data as an array of bars. 

* {{color|blue|BarPriceLevels[] Data2 { get; }}} – returns an array of downloaded price levels.

*{{color|blue|InstrumentDataRequest Request { get; }}} – is used in DataLoader. This attribute helps to make the same request for DataLoader that is used for the instrument bars. 

* {{color|blue|Bar? RTData { get; set; }}} – returns realtime data (if available).

* {{color|blue|BarPriceLevels? RTData2 { get; set; }}} – returns realtime price levels (if available) 

* {{color|blue|DataLoadedEvent Event { get; }}} – returns a reason for calling the callback function 

* {{color|blue|LoadDataCallback}}. Available values are None, History, RTUpdateLastBar, and RTNewBar.
  

To cancel data downloading the void EndLoadData(IDataLoaderResult Result) method should be called. The Result of BeginLoadData call should be put into the argument as an attribute.