Cannot extend DrawObjects.Line

[gripload]

Hello,

I'm trying to create a new class to extend the DrawObjects.Line class using inheritance. Here's the code for the extended class:

		public enum TrendlineType {
			PrimaryTrend,
			PrimaryChannel,
			SecondaryTrend,
			SecondaryChannel,
			CounterTrend,
			CounterChannel
		}
			
	    public class Trendline : NinjaTrader.NinjaScript.DrawingTools.Line
	    {
	        public Trendline() : base()
	        {
					
	        }
			public TrendlineType Type() 
			{
				return TrendlineType.PrimaryTrend;
			}
				
	    }

However, when I try and cast an object of type DrawingObjects.Line, I get the error:

Unable to cast object of type 'NinjaTrader.NinjaScript.DrawingTools.Line' to type 'Trendline'.

				NinjaTrader.NinjaScript.DrawingTools.Line objLine = objTool as DrawingTools.Line;
																
				Trendline objTrendline = (Trendline)new DrawingTools.Line(); // This raises a casting error

Please let me know if you have any ideas. A full indicator that illustrates the problem is attached. Place the indicator on a chart that has at least one manually drawn trendline, and the error can be seen in the NinjaScript Output window.

Thank you,

Ryan

[NinjaTrader_JessicaP]

Hello gripload, and thank you for your questions.

Generally the best way to resolve this scenario, where you would like to downcast a NinjaTrader Line into a TrendLine, is with a static factory method in your TrendLine class with the signature

[FONT=Courier New]public static Trendline newFromLine(NinjaTrader.NinjaScript.DrawingTools.Line line)
[/FONT]

You could also simply take in a line as a constructor to a Trendline; there are many ways to implement this. One way or the other, though, you will have to tell C# exactly how to turn a Line into a more specific kind of Line.

I am including a publicly available link to a Stack Overflow discussion on this topic. Please let us know if there are any other ways we can help.

http://stackoverflow.com/questions/1524197/downcast-and-upcast