What Is A Null Error in Code Execution





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null error in code execution
In my past few years of experience in coding, many times, I have faced the exception for passing on Null
values. Due to which, the compiler or the machine throws this exception out to the screen.
System.NullReferenceException
Actually, many times, this case has been discussed by other professional developers and part-time developers and they’ve provided the solution to this many times that I think, if you just close your eyes and go for the solution, you’ll find it on the very 3rd web page for the tutorial websites.
System.NullReferenceException is the exception raised when you try to dereference a null object. Read the post for more information on that.
What Actually Is This Error?
This error occurs when you’re passing on a null
value. A null
value means that there is actually no value in this variable. It's not even a zero. String
is the major case for this exception because other variables sometimes get a zero value, and hide this error. Arrays give out this error, when they’re empty. So in general, anything that has no value, is called to have a null
value.
Null
means that the object doesn’t exist.If you read this MSDN post, you will get the understanding of the concept of null
, how they’re created in programming, how they’re a cause of an error in programming.
Why Does This Error Come Up?
This error generally comes up when you’re trying to pass a null
value as an argument (parameter) to a method (function) that needs an active parameter to work on. When the parameter being passed is empty, null
it throws this error telling the developer that the variable that he passed is zero.
You can take the example of a shopkeeper. You ask him to give you a packet of biscuits, but you don’t pay him. What would he do? He’d shout at you like, ‘Hey, you didn’t pay for the biscuits!’. This thing is exactly like that. You don’t pass any value and the compiler complains to you in this manner, telling you that you’ve provided him with nothing.
In programming, many functions or properties accept an argument to work on. For example, take an example of the following code:
int myVar = null;
// use the myVar in some methods etc
Once this code executes, the myVar
is more likely to raise the NullReferenceException
in your program execution.
NullReferenceException
being raised in an application. Object reference not set to an instance of object means that the reference does not exist.Empty lists, empty string
s are an example of objects that might trigger a null
reference exception in your software applications.
How To Handle This Error?
There are many ways of doing this. You can either use a try catch
block to see what is the error and then handle it. You can either use a simple condition operator (if else
, in this scenario) to detect the value and then do respectively. Or you can use your own idea to check the value is not null
. Or you can even prompt the user to enter the value, otherwise don’t trigger the function at all. Or…you can do anything.
Usually, you handle all type of exceptions in your software, to minimize any possible condition that would stop the program execution and would break the application causing a bad user experience.
Here are a few samples for that.
Using a Try Catch Block
A try catch
block is a simple block of code, which executes a block of code in the try
part and if there is an error in the code, it passes that error to the catch
block for the developer to handle it in a user friendly manner.
try
{
// your source code here...
// that would trigger the exception
}
catch (System.NullPointerException e)
{
Console.Write("There was a raised error in your code.");
}
In the above example, the catch
block would execute if the variable being used was empty. If there would have been some value, the array would have value thus preventing the error. Somehow, even if there is an error in your code, the application won’t break but will show an error message to the user. Which is helpful for creating enterprise software, where software loads a lot of data before creating the UI and loading to let the user start using it.
This MSDN post shows the concept of a try catch
structure in programming.
Flowchart for a try catch
structure is as follows:
try catch
block.if else Block
This block is the basic block of the conditional operation. It checks for a value, and executes either one depending on the true
or false
result of a condition. It is pretty handy and short for those who don’t have to work with errors, but just with values and condition.
if(something != null) { // check for value null
Console.Write("Not null! String is " + something);
} else {
Console.Write("Whoops! Null exception.");
}
See, this was pretty easy to handle. Using this structure, you allow the user to do whatever he wants to do. But you move down to the critical stages only if the user has provided enough details for the software to work on.
This if else
block checks for the value, if the condition is met (the value is provided), then it will execute the code, otherwise the second block of code would be executed.
Still remember, that if else
blocks do not prevent any error chances if
just checks for the value. It is not a good approach to minimize the null
reference exception using an if else
block. But programmers usually use it instead of try catch
. But the best method of catching exceptions of any kind is to use the try catch
block. It allows you to capture all of the exceptions that are raised in the application and do programming according.
This MSDN post explains if else
structure.
Flowchart for if else
block is as:
If else
is just used to check a condition.Remedies
Now there are some other ideas and logic to work with the code and prevent this error from happening. One of them is to always ask for the value and then continue, if user doesn’t provide the value, keep him prompted that once he adds value, only then can he use that particular feature and all that stuff. Otherwise, just to prevent the error, don’t show stuff to the user.
For example, the following UI is useful to get the values from the user. Until he doesn’t provide any value, either continue to how that error message or just try to disable any button or control that would trigger the function to get the values from the controls and work on them.