How to use break?

Question

Hello,

I am trying to figure out why i get this message error:

Error on calling 'OnRender' method on bar 513: Object reference not set to an instance of an object.

My chart has 513 bars in it. I loop throught all the bars of the chart and create a new series of values (candle).

  int index;
                    int LastIndexChecked = 0;
                    double sum = 0;

for(int barIndex = LastIndexChecked; barIndex <= CurrentBar; barIndex++)
                    {
                    double closePrice16 = Bars.GetClose(barIndex);
                    double openPrice9 = Bars.GetOpen(barIndex+1);
                    double closePrice = Bars.GetClose(barIndex+1);

                    double difCP = closePrice16 - openPrice9;

                    index = barIndex;


                    sum += difCP;

                    double candle = closePrice + sum;



                         Value[0] = candle;

I think somehow a break should be introduce to stop the loop at 513. Every minute a new bar is added in the chart, making the chart bars increase to 514, 515 ...

After a moment my indicator vanish from the chart. If i introduce a break after Value[0] i get a straight line in the chart.

Anyone has an idea where and how to introduce the break statement, if only that is the solution to my problem. Could be Value[0] as well but i am not sure what it is going to change.

Thank you

Answer 1

You can set a break-point, hover over the break-point for the following

Click the gear and set a condition and under Actions uncheck "Continue Execution".

When hit, hover over variables to see what the problem is.

Answer 2

You should use try {} catch {}. In the catch block you can show relevant information. You could then continue the program or exit the program. Tell us if you need details.

Use of try {} catch {} is very useful for diagnostic purposes but it should be used for production code too.

Answer 3

Hello,

The following are basic/simple which you should be able to use in tangent with my first reply or without my first reply.

In regards to try/catch

Basic try/catch

try  
{  
    var fileContents = File.ReadAllLines("NonExistingFile.txt");  
}  
catch (Exception exception)  
{  
    MessageBox.Show($"We encountered issues\n{exception.Message}");  
}  

Using named tuples

private (List<string> lines, bool success, Exception exception) ReadSomeFile()  
{  
    List<string> contents = new List<string>();  
  
    try  
    {  
        var fileContents = File.ReadAllLines("NonExistingFile.txt");  
        return (lines: contents, success: true, exception: null);  
    }  
    catch (Exception ex)  
    {  
        return (lines: contents, success: false, exception: ex);  
    }  
  
}  

Usage

var (lines, success, exception) = ReadSomeFile();  
if (success)  
{  
    foreach (var line in lines)  
    {  
          
    }  
}  
else  
{  
    MessageBox.Show($@"Encountered issues {exception.Message}");  
}  

Logging

This is a homebrewed logging class and there are many loggers on the web, this one keeps things simple that knows were the exception was but not the line number. I keped it simple on purpose.

using System;  
using System.Diagnostics;  
using System.Runtime.CompilerServices;  
  
namespace HandleExceptionsSimple  
{  
    public static class Logger  
    {  
        private static TextWriterTraceListener _textWriterTraceListener;  
        public static void CreateLog()  
        {  
            _textWriterTraceListener = new TextWriterTraceListener(  
                "applicationLog.txt",   
                "PayneListener");  
              
            Trace.Listeners.Add(_textWriterTraceListener);  
        }  
        public static void Close()  
        {  
            _textWriterTraceListener.Flush();  
        }  
        public static void Exception(string message, [CallerMemberName] string callerName = null) =>   
            WriteEntry(message, "error", callerName);  
          
        public static void Exception(Exception ex, [CallerMemberName] string callerName = null) =>   
            WriteEntry(ex.Message, "error", callerName);  
          
        public static void Warning(string message, [CallerMemberName] string callerName = null) =>   
            WriteEntry(message, "warning", callerName);  
          
        public static void Info(string message, [CallerMemberName] string callerName = null) =>   
            WriteEntry(message, "info", callerName);  
          
        public static void EmptyLine() => _textWriterTraceListener.WriteLine("");  
  
        private static void WriteEntry(string message, string type, string callerName)  
        {  
            _textWriterTraceListener.WriteLine($"{DateTime.Now:yyyy-MM-dd HH:mm:ss},{type},{callerName},{message}");  
  
        }  
    }  
}  

Usage

try  
{  
    var fileContents = File.ReadAllLines("NonExistingFile.txt");  
}  
catch (Exception exception)  
{  
    Logger.Exception(exception);  
    Logger.Close();  
}  

Then there is global unhandled exception handling, see my NuGet package where documentation is under Prerequires.