How to get sum of all parent and child elements in linq?

Question

User-1564432484 posted

I have records of parent elements which also have child elements. Parent as well as child has ExtendedListPrice field. I need to show sum of this field whether the data is of Parent or child. How to achieve this? Shall I first get the total of all Parent elements and then add sum of all child elements?

Answer 1

User1120430333 posted

How to achieve this? Shall I first get the total of all Parent elements and then add sum of all child elements?

That's how you do it. 1 parent value + add sum of all children using the Sum() aggregate. 

Answer 2

User1520731567 posted

Hi rameezshaikh56,

hall I first get the total of all Parent elements and then add sum of all child elements?

I think so,I suggest you could use SelectMany() and Sum() to get all child elements' sum firstly, then get all parent elements' sum by the same way.

For example:

  var  total = (from user in db.authors
                         from books in user.book
                         select (int?)books.Id).Sum() ?? 0;

Note: the SUM in SQL over 0 rows is NULL, not 0

or as lambdas (from comments):

var total = db.authors.SelectMany(user => user.book).Sum(books=> (int?)books.Id) ?? 0;

I find the similar question from this link,you could refer to it:

https://stackoverflow.com/questions/5893445/sum-nested-values-with-linq

Best Regards.

Yuki Tao