Help with "Object reference not set" error in OnBarUpdate()

[MarkWise]

Hello!

I'm new to NinjaTrader*(as a convert from FXCM) and am converting my indicators from Lua to C#. I'm getting a handle on things for the most part, but apparently still have confusion with the way bar timing works.

I have a "trend state" indicator being consumed by another indicator and receive the following error:
Indicator 'TrendState': Error on calling 'OnBarUpdate' method on bar 50: Object reference not set to an instance of an object.

The TrendState indicator works just fine on its own. I know I'm close but have something not quite right. The code is below. I tried to follow how the @ATR, but can't figure this out for the life of me.

What am I missing or doing wrong?

		//
		// PARENT INDICATOR CODE
		//
        protected override void OnStateChange()
        {
            if (State == State.SetDefaults)
            {
                Description = @"My Description";
                Name = "TrendState";
                Calculate = Calculate.OnEachTick;
                IsOverlay = true;

                DisplayInDataBox = true;
                PaintPriceMarkers = false;
                DrawHorizontalGridLines = false;
                DrawVerticalGridLines = false;

                ScaleJustification = NinjaTrader.Gui.Chart.ScaleJustification.Right;
                IsSuspendedWhileInactive = true;

                AddPlot(ChartControl.Properties.ChartBackground, "TrendState");
            }
        }
        protected override void OnBarUpdate()
        {
            if (CurrentBar < 50)
            {
				// Need at least 50 bars to work properly, so return "undetermined" state
                Value[0] = 0;
                return;
			}
			else
			{
				// Get the state of the trend
				Value[0] = DoSomeLogicThatDeterminesState();
				
				// Do some visual UI stuff here to represent state
			}
		}		

		
		//
		// CONSUMING INDICATOR CODE
		//
		protected override void OnBarUpdate()
		{
            Print("Candle closed; Opened at: " + Time[0].ToString() + "; CurrentBar: " + CurrentBar + "; O: " + Open[0] + "; C: " + Close[0] + "; H: " + High[0] + "; L: " + Low[0] + "; State: " + State.ToString());

            double state = TrendState()[0];
            Print(String.Format("Current State: {0}", state));
        }

[NinjaTrader_AlanP]

Hello MarkWise,

Thank you for your note.

If you add a current bar check to the hosting indicator, do you still experience the issue?

For example,

protected override void OnBarUpdate()
{
if (CurrentBar < 50) return;

Print("Candle closed; Opened at: " + Time[0].ToString() + "; CurrentBar: " + CurrentBar + "; O: " + Open[0] + "; C: " + Close[0] + "; H: " + High[0] + "; L: " + Low[0] + "; State: " + State.ToString());

double state = TrendState()[0];
Print(String.Format("Current State: {0}", state));
}

I look forward to your reply.

[MarkWise]

I do actually. If you look at the OnBarUpdate() method in my sample code, I'm doing the following:

     if (CurrentBar < 50)
            {
	       // Need at least 50 bars to work properly, so return "undetermined" state
                Value[0] = 0;
                return;
	}
	else
	{
		// Get the state of the trend
		Value[0] = DoSomeLogicThatDeterminesState();
				
		// Do some visual UI stuff here to represent state
	}

[tradesmart]

What happens when CurrentBar = -1?

It's less than 50, so you're trying to assign a value to a bar that does not exist yet, i.e., at index 0.

Therefore, Value[0] cannot be set to anything. You might try commenting out that line or at least check to see that CurrentBar >=0 before assigning a value.

[NinjaTrader_AlanP]

Hello,

Thank you tradesmart.

MarkWise, Please replace what you have in your current bar check with,

if (CurrentBar < 50) return;

In both your hosted and hosting indicator and let us know if that fails to resolve the issue.

Please let us know if you need further assistance.

[MarkWise]

Solved!

So after much debugging I realized what the issue is...

The indicator I was calling also does some UI manipulation. In that logic, I was referencing the "ChartControl" object which apparently doesn't exist unless the indicator is actually sited on the chart itself.

By simply wrapping the UI logic in a "if (ChartControl != null) ..." block, I was able to solve the issue.

Thanks everyone for your responses!!!!