How to create a Custom Class?

[poseidon_sthlm]

Hi!
I'v tried to create a custom class "Top_Bottom" for my indicator. The code compiles. But when I add the indicator to a chart i get the error message "Object reference not set to an instance of an object."
I'v identified the line in the code below that causes the error. But I'm not sure how to adjust the code. Is it sufficient to add the variables (double v, double l, int b) like I'v done in the class or do I have to add them to the Variabels region and Properties region too?

#region Using declarations

using System.Collections.Generic;

#endregion


    { 
        #region Variables

        private double x;
        private double y;
        
        private List< Top_Bottom  > DTlist;
        
        #endregion

        
        protected override void Initialize()
        {
            List< Top_Bottom  > DTlist = new List< Top_Bottom  >();
        }

       
        protected override void OnBarUpdate()
        {                    
            // This line causes the error. Add DT to dynamic list
           [B][COLOR=Red] DTlist.Add(new Top_Bottom(x, y, CurrentBar));  [/COLOR][/B]                          
        }
        
        // My Custom Class
        public class Top_Bottom
        {
            // Constructor
            public Top_Bottom(double v, double l, int b)
            {
                this.Value = v;
                this.Line = l;
                this.BarNo = b;
            }

            public double Value { get; set; }
            public double Line { get; set; }
            public int BarNo { get; set; }
        }

/Best regards

[NinjaTrader_Tim]

Hi poseidon_sthlm,

Creating a custom array list is, unfortunately, something I cannot provide support for.

However, as a hint, you will need to ensure the array or any object within is not empty, when you try to access/call it.