Try/Catch Method Challenge/Mistery

July 17th, 2018, 05:18 PM

Hi guys

I am trying to write/delete a file couple of times per minute. I have try/catch inside code but my strategy keeps getting stopped with the following error:

Code

Error:elsystem.NullObjectException: Object Reference not set to an instance of an object. Call Stack: MyStrat.myf_writetofile()

The strategy runs couple of days, then suddenly shuts down
can anyone spot what is the issue here? Been trying for couple of months to figure it out. It usually stop at elsystem.io.StreamWriter.Create step. The file it tried to create could be accessed by other software.

BUT - the MAIN question here is why Try Catch not working? it just avoids it and stops the strategy, Really getting crazy here

Code

Try	
Begin
    			file = elsystem.io.StreamWriter.Create("C:\........\Files\Final.csv");    			
    	End;	
    Catch (elsystem.NullObjectException ex)	Begin						 
				Print(" File Create +" + ex.ToString()+" MSG: "+ex.Message.ToString()+" Type "+ex.InnerException.ToString());						
			End;
	Catch (elsystem.io.IOException ex1)	Begin						 
				Print(" File Create IO Except +" + ex1.ToString()+" MSG: "+ex1.Message.ToString()+" Type "+ex1.InnerException.ToString());						
			End;			
    End;
    
    
    Try	Begin
    			file.Write(NewGDtoFile);    			
    	End;	
    Catch (elsystem.NullObjectException ex)	Begin						 
				Print(" File Write +" + ex.ToString()+" MSG: "+ex.Message.ToString()+" Type "+ex.InnerException.ToString());						
			End;
	Catch (elsystem.io.IOException ex1)	Begin						 
				Print(" File Write IO Except +" + ex1.ToString()+" MSG: "+ex1.Message.ToString()+" Type "+ex1.InnerException.ToString());							
			End;			
    End;
    
   
    Try	Begin
    			file.Close();    			
    	End;
    Catch (elsystem.NullObjectException ex)	Begin						 
				Print(" File Close NULL +" + ex.ToString()+" MSG: "+ex.Message.ToString()+" Type "+ex.InnerException.ToString());						
			End;		
    Catch (elsystem.io.IOException ex1)	Begin						 
				Print(" File Close IO Except " + ex1.ToString()+" MSG: "+ex1.Message.ToString()+" Type "+ex1.InnerException.ToString());						
			End;	
    End;

Thank You

July 17th, 2018, 09:44 PM

Very generically I can tell you that you are hitting a null value error. So you need to check and make sure your variable / object is not null before you call it.

For example this throws an error:

double testvariable = 0;

testvariable = null;

if (testvarialbe > 1)
{
// do something
}

So you have to check if it is null first before you evaluate it.

I am not sure where you are hitting your error in your code:
"Error:elsystem.NullObjectException: Object Reference not set to an instance of an object." But whatever line is throwing this error, just check your variable to make sure it is not null and you should be fine.

Happy Coding!

Ian

eronyx

Hi guys

I am trying to write/delete a file couple of times per minute. I have try/catch inside code but my strategy keeps getting stopped with the following error:

Code

Error:elsystem.NullObjectException: Object Reference not set to an instance of an object. Call Stack: MyStrat.myf_writetofile()

The strategy runs couple of days, then suddenly shuts down
can anyone spot what is the issue here? Been trying for couple of months to figure it out. It usually stop at elsystem.io.StreamWriter.Create step. The file it tried to create could be accessed by other software.

BUT - the MAIN question here is why Try Catch not working? it just avoids it and stops the strategy, Really getting crazy here

Code

Try	
Begin
    			file = elsystem.io.StreamWriter.Create("C:\........\Files\Final.csv");    			
    	End;	
    Catch (elsystem.NullObjectException ex)	Begin						 
				Print(" File Create +" + ex.ToString()+" MSG: "+ex.Message.ToString()+" Type "+ex.InnerException.ToString());						
			End;
	Catch (elsystem.io.IOException ex1)	Begin						 
				Print(" File Create IO Except +" + ex1.ToString()+" MSG: "+ex1.Message.ToString()+" Type "+ex1.InnerException.ToString());						
			End;			
    End;
    
    
    Try	Begin
    			file.Write(NewGDtoFile);    			
    	End;	
    Catch (elsystem.NullObjectException ex)	Begin						 
				Print(" File Write +" + ex.ToString()+" MSG: "+ex.Message.ToString()+" Type "+ex.InnerException.ToString());						
			End;
	Catch (elsystem.io.IOException ex1)	Begin						 
				Print(" File Write IO Except +" + ex1.ToString()+" MSG: "+ex1.Message.ToString()+" Type "+ex1.InnerException.ToString());							
			End;			
    End;
    
   
    Try	Begin
    			file.Close();    			
    	End;
    Catch (elsystem.NullObjectException ex)	Begin						 
				Print(" File Close NULL +" + ex.ToString()+" MSG: "+ex.Message.ToString()+" Type "+ex.InnerException.ToString());						
			End;		
    Catch (elsystem.io.IOException ex1)	Begin						 
				Print(" File Close IO Except " + ex1.ToString()+" MSG: "+ex1.Message.ToString()+" Type "+ex1.InnerException.ToString());						
			End;	
    End;

Thank You

ABCTG · July 18th, 2018, 04:00 AM

eronyx,

did you post the entire method code? What happens if you place your method call inside a try catch statement, without trying to catch a specific exception?

Code

try
 myf_writetofile() ; //your method in here
catch (elsystem.exception ex)
   Print("ex = " + ex.ToString());
end ;

Regards,

ABCTG

eronyx

Hi guys

I am trying to write/delete a file couple of times per minute. I have try/catch inside code but my strategy keeps getting stopped with the following error:

Code

Error:elsystem.NullObjectException: Object Reference not set to an instance of an object. Call Stack: MyStrat.myf_writetofile()

The strategy runs couple of days, then suddenly shuts down
can anyone spot what is the issue here? Been trying for couple of months to figure it out. It usually stop at elsystem.io.StreamWriter.Create step. The file it tried to create could be accessed by other software.

BUT - the MAIN question here is why Try Catch not working? it just avoids it and stops the strategy, Really getting crazy here

Code

Try	
Begin
    			file = elsystem.io.StreamWriter.Create("C:\........\Files\Final.csv");    			
    	End;	
    Catch (elsystem.NullObjectException ex)	Begin						 
				Print(" File Create +" + ex.ToString()+" MSG: "+ex.Message.ToString()+" Type "+ex.InnerException.ToString());						
			End;
	Catch (elsystem.io.IOException ex1)	Begin						 
				Print(" File Create IO Except +" + ex1.ToString()+" MSG: "+ex1.Message.ToString()+" Type "+ex1.InnerException.ToString());						
			End;			
    End;
    
    
    Try	Begin
    			file.Write(NewGDtoFile);    			
    	End;	
    Catch (elsystem.NullObjectException ex)	Begin						 
				Print(" File Write +" + ex.ToString()+" MSG: "+ex.Message.ToString()+" Type "+ex.InnerException.ToString());						
			End;
	Catch (elsystem.io.IOException ex1)	Begin						 
				Print(" File Write IO Except +" + ex1.ToString()+" MSG: "+ex1.Message.ToString()+" Type "+ex1.InnerException.ToString());							
			End;			
    End;
    
   
    Try	Begin
    			file.Close();    			
    	End;
    Catch (elsystem.NullObjectException ex)	Begin						 
				Print(" File Close NULL +" + ex.ToString()+" MSG: "+ex.Message.ToString()+" Type "+ex.InnerException.ToString());						
			End;		
    Catch (elsystem.io.IOException ex1)	Begin						 
				Print(" File Close IO Except " + ex1.ToString()+" MSG: "+ex1.Message.ToString()+" Type "+ex1.InnerException.ToString());						
			End;	
    End;

Thank You

ABCTG · July 18th, 2018, 04:28 AM

eronyx

BUT - the MAIN question here is why Try Catch not working? it just avoids it and stops the strategy, Really getting crazy here

Hi eronyx,

the error is most likely not caused due to the try statement failing here, but due to ex.InnerException or ex1.InnerException causing the error in your print statement. When you check the below code, you will find it raises a similar error message:

Code

once
begin
	try
  	
  	Value2 = 2 ;
  	Value3 = 1 ;
  	
  	Value1 = 1 / ( Value2 - Value3 - 1 ) ;
	
	catch (elsystem.exception ex)
		Print( "ex = " + ex.ToString() + "; ex.Message = " + ex.Message + "; InnerException = ", ex.InnerException.ToString() ) ;
	end ;
end ;

Removing ex.InnerException from the print will result in the code getting executed without the error message i.e. the DivideByZeroException getting caught and the print out to appear. The same is probably true for your code, too.
The fix for your code should be to check that the InnerException is not null before you print it. So something along the lines of

Code

if ex.InnerException <> null then
	Print( "ex = " + ex.ToString() + "; ex.Message = " + ex.Message + "; InnerException = " + ex.InnerException.ToString() ) 
else
	Print( "ex = " + ex.ToString() + "; ex.Message = " + ex.Message + "; InnerException = null" ) ;

should prevent the error.

Regards,

ABCTG

July 18th, 2018, 05:26 AM

This is the line where it stops

file = elsystem.io.StreamWriter.Create("C:\........\Files\Final.csv");

it's like at some point it can't delete/create file again and gives this error, then works fine 3-5 days(writing this file few times per minute) then again stops here.

I am not even able to do the if (file> 1) as you suggested or something because it stops right there.

iantg

Very generically I can tell you that you are hitting a null value error. So you need to check and make sure your variable / object is not null before you call it.

For example this throws an error:

double testvariable = 0;

testvariable = null;

if (testvarialbe > 1)
{
// do something
}

So you have to check if it is null first before you evaluate it.

I am not sure where you are hitting your error in your code:
"Error:elsystem.NullObjectException: Object Reference not set to an instance of an object." But whatever line is throwing this error, just check your variable to make sure it is not null and you should be fine.

Happy Coding!

Ian

July 18th, 2018, 05:30 AM

Thank You ABCTG, that indeed could be issue, is like it is not stopping at the try catch, but at that print method alone.

tricky tricky. Good catch !!!

Thanks again, I will also try placing the entire method in try catch if this does not work.

ABCTG

Hi eronyx,

the error is most likely not caused due to the try statement failing here, but due to ex.InnerException or ex1.InnerException causing the error in your print statement. When you check the below code, you will find it raises a similar error message:

Regards,

ABCTG

Try/Catch Method Challenge/Mistery

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Try/Catch Method Challenge/Mistery