C# - Group Objects by Property Value

Question

I have a console app written in C#. In my app, I have an object defined like this:

public class Order
{
  public double Price { get; set; }

  public string Description { get; set; }

  public int ItemCount { get; set; }
}

I have the Order objects in a List<Order>. I need to group these Orders by their Price. But, the groups represent a price range. For example, I want the following groups:

$0 - $10
$10 - $20
$20 - $30
$30 - $40
$40 - $50
$50 - $60
$60 - $70
$70 - $80
$80 - $90
$90 - $100

Originally, I was going to just loop through the List<Order>, but it seemed clunky. I felt this was a good case for Linq, but I've come up short. My approach isn't working.

Is there a way to group the orders into $10 increments based on the Price property with LINQ?

http://stackoverflow.com/questions/13828216/group-by-range-using-linq — Nard Dog, Apr 11 '17 at 18:18
What about giving the class a `GetGroup()` method and group by that value? If the grouping logic can be defined by class, that is. — ChriPf, Apr 11 '17 at 18:20
Group ranges are incorrect as they overlap, where does $10 comes in 0-10 or 10-20, you need to create exclusive ranges — Mrinal Kamboj, Apr 11 '17 at 19:01

score 5 · Accepted Answer · answered Apr 11 '17 at 18:21

5

This should work : var groups = orders.GroupBy(order => order.Price - order.Price % 10);

answered Apr 11 '17 at 18:21

Toto

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1

Due to the idiosyncrasies of how doubles work and the fact that a `GroupBy` does a `.Equals(` comparison to make its groups I would be careful of this answer. When dealing with larger numbers you may end up with groups with a fraction of a cent assigned to them. – Scott Chamberlain Apr 11 '17 at 18:23
Meh, I ran some tests, I could not get it to fail on any number between `0` and `Int32.MaxValue`. I also tried `Int64.MaxValue`, `Int64.MaxValue-1`, `Double.MaxValue`, and `Double.MaxValue - 1.2` and those did not fail either. I think for most reasonable uses this method is fine to do. – Scott Chamberlain Apr 11 '17 at 18:43
Why does $10 belongs to 0-10 not 10-20 ? – Mrinal Kamboj Apr 12 '17 at 01:28

score 4 · Answer 2 · answered Apr 11 '17 at 18:17

4

Use integer arithmetic and GroupBy, for example:

orders.GroupBy(o => (int)o.Price / 10)

answered Apr 11 '17 at 18:17

driis

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C# has a `%` modulo operator. – Asad Saeeduddin Apr 11 '17 at 18:18
4

@AsadSaeeduddin so? I don't see how the modulo operator would be useful here. – Scott Chamberlain Apr 11 '17 at 18:19
2

Nevermind, [Toto's answer](http://stackoverflow.com/a/43353494/80274) showed how you could use it. – Scott Chamberlain Apr 11 '17 at 18:22

C# - Group Objects by Property Value

2 Answers2