The inconsistent feeling about Null handling between LinQ and computed property

Question

There is one typical scenario: parent- child summary calculation.

There are usually existing two level summary calculation.  

1 the sum between the different child columns. 

 result = this.fee1+ this.fee2;

2 the sum about the child rows.

result = this.OrderDetail.Sum(d => d.SubCost);

The fact is:  

sum 2 runs like the SQL way, it omits all the null value, and give me the correct number.

sum 1 runs like the .net way ,  if there exist any null value, there are no result.

My question: Is there existing any elegant style to handling sum 1 calculation?

Perhaps, LS team could  add one method like .SafeValue() , which can provide the same function like

(value.HasValue? value:0)

Answer 1

There is already something you can use for that. It's called GetValueOrDefault. It only applies to nullable properties.

It does exactly what you describe.

So your code would read:

result = this.fee1.GetValueOrDefault+ this.fee2.GetValueOrDefault;

---

Yann - LightSwitch Central - Click here for FREE Themes, Controls, Types and Commands

If you find a reply helpful, please click "Vote as Helpful", if a reply answers your question, please click "Mark as Answer"

By doing this you'll help people find answers faster.

Answer 2

Wow, it works fine! Which this candy, it can save me a lot of time to struggle with the type safe issue and focus on the real calculation again!

Thanks a lot , Yann!