Check the objects properties are null

Question

I have a class which gets a object from the external system. I want to validate my parameters are correct. It seems my object is not null even though I sent a wrong value to the service.Basically I want to check mySalesOrderHeader contains a valid order number or not.

For example, if (mySalesOrderHeader != null) { Do My Stuff} I am checking this condition once mySalesOrderHeader is retrieved from the system. Inside my if condition[Where {Do My Stuff}] is located, I am accessing its property and checking its existence.

if(string.IsNullOrEmpty(mySalesOrderHeader.OrderNumber)){}

But in here it throws a null reference exception. How can I check a property is null, if my parent object does not have the value in it.

Note: I am using C# 3.0

Possible duplicate of [What is a NullReferenceException, and how do I fix it?](https://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — Lance U. Matthews, Jun 24 '17 at 18:30
Have you checked how the property getter is build? Maybe it is the getter that is throwing exception not mySalesOrderHeader. — Pablo notPicasso, Jun 24 '17 at 19:05

score 3 · Answer 1 · answered Jun 24 '17 at 18:15

3

If the variable mySalesOrderHeader is null, you cannot access its properties otherwise exception will be thrown. So, you should check mySalesOrderHeader first.

if  (string.IsNullOrEmpty(mySalesOrderHeader != null ? mySalesOrderHeader.OrderNumber : null))
{
...
}

answered Jun 24 '17 at 18:15

Tuan Le PN

364
1
12

Thanks Tuan. It seems mySalesOrderHeader is not null but I cannot access the mySalesOrderHeader.OrderNumber property. It throws a null reference exception. – SPKan Jun 24 '17 at 19:03
@SPKan Then you need to include the code for that property in your question. – mason Jun 24 '17 at 19:04

Salah Akbari · Accepted Answer · 2017-06-24T18:21:27.183

2

Use Null-Conditional operator (C#6 feature). It tests for null before performing a member access Like this:

if (string.IsNullOrEmpty(mySalesOrderHeader?.OrderNumber))
{
}

edited Jun 24 '17 at 18:21

answered Jun 24 '17 at 18:10

Salah Akbari

39,330
10
79
109

Thanks @Akbari. but I am using c# 3.0. It seems mySalesOrderHeader is not null but I cannot access the mySalesOrderHeader.OrderNumber property. – SPKan Jun 24 '17 at 19:02

score 1 · Answer 3 · answered Jun 24 '17 at 19:03

You can try below snippet. Its easy and clean and would work with C# 3.0

if (mySalesOrderHeader != null)
{
    // are you sure you're not missing out '!' operator at string null or empty check?
    if  (!string.IsNullOrEmpty(mySalesOrderHeader.OrderNumber))
    {
        // logic if order number has some value
    }
}

Also only check for parent object once its retrieved (to me it seemed from your question that the null check is bypassed due to some reason.)

Check the objects properties are null

3 Answers3