How can i get my application to accept null value as valid

I have a C#  application with a variable  selectedPeriod.mnthyear

I need to have the variable accept both regular values and Null

The test  script (attached)  is ok when there is a value.

When the value of the variable  is null  the application  reports an error as attached

What is wrong with my test syntax for   selectedPeriod.mnthyear  when it is null ?

Thanks

Olukay
HandlingNull16022019.PNG
Olukayode OluwoleSystems AnalystAsked:
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David Johnson, CD, MVPRetiredCommented:
I would use a try/catch block to trap these errors.
Chinmay PatelChief Technology NinjaCommented:
You should use Nullable Types https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/nullable-types/
double? pi = 3.14;
char? letter = 'a';

int m2 = 10;
int? m = m2;

bool? flag = null;

// Array of nullable type:
int?[] arr = new int?[10];

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Gustav BrockCIOCommented:
Don't check for a property of selectedPeriod but for the object itself, thus:

If (selectedPeriod == null)
{
// <snip>

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Chris StanyonWebDevCommented:
Couple of points to clarify here.

When you are doing this:

if (selectedPeriod.mnthyear == null)

You are looking to check if the mnthyear property of the selectedPeriod object is null. The error you're getting is telling you that the selectedPeriod object is null. Because that's null, it throws and error and never actually gets to check the mnthyear property (you can't check the property of a null).

You should use the null-conditional operator here (the question mark), like so:

if (selectedPeriod?.mnthyear == null)

Now your check will return null if selectedPeriod is null. If it's not, then it will check the mnthyear. This will prevent the error you're getting, and match null if either selectedPeriod or mnthyear is null.

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Olukayode OluwoleSystems AnalystAuthor Commented:
A big thank you to all the experts.

I believe any of the suggestions might have worked.

The solution from Chris Stanyon requiring only a  ?   appears easiest to implement

Once again thanks  for the help
Gustav BrockCIOCommented:
But you don't use the property mnthyear in this part of the code, so easiest ..?
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