How can I get totals for more than one column in a list and put this into an object using LINQ?

Question

How can I get a total of the count of some columns in a list using LINQ and put this into an object?

I have a list that

List<History> a = getTodayData();

where my class History looks like this:

public class History
{
    public Int32 Id { get; set; }
    public string YYMMDD { get; set; }
    public int Quiz { get; set; }
    public int Views { get; set; }
    public int Clicks { get; set; }
    public int Points { get; set; }
}

What I would like is to populate this object with the totals for each of Views, Clicks and Points.

public class Today
{
    public int Views { get; set; }
    public int Clicks { get; set; }
    public int Points { get; set; }
}

Some help / advice would be much appreciated.

Possible duplicate of [Multiple SUM using LINQ](https://stackoverflow.com/questions/1704225/multiple-sum-using-linq) — Drag and Drop, Nov 05 '18 at 13:47

Sefe · Accepted Answer · 2018-11-05T13:39:08.870

5

With LINQ you can simply calculate the sums separately:

Today today = new Today {
    Views = a.Sum(history => history.Views),
    Clicks = a.Sum(history => history.Clicks),
    Points = a.Sum(history => history.Points),
}

In the most unlikely event you run into performance issues with this solution, you can always use a non-LINQ foreach loop:

Today today = new Today();
foreach(History history in a) {
    today.Views += history.Views;
    today.Clicks += history.Clicks;
    today.Points += history.Points;
}

edited Nov 05 '18 at 13:39

answered Nov 05 '18 at 13:32

Sefe

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No, not a typo, this is correct C# and will compile fine. – Sefe Nov 05 '18 at 13:57
Sure but.. Ok I have Comma leftover OCD. `var trigger = new [] {1,};` – Drag and Drop Nov 05 '18 at 14:02
I routinely put a comma in these cases simply because more often than never, you extend initialization by a few properties later. And adding the comma later is cumbersome. – Sefe Nov 05 '18 at 14:16

score 1 · Answer 2 · answered Nov 05 '18 at 13:49

Use this one and let me know if it is work for you or not.

List<History> a = getTodayData();
 Today t = new Today
           {
            Clicks = a.Sum(h => h.Clicks),
            Views=a.Sum(h=>h.Views),
            Points=a.Sum(h=>h.Points)
        };

How can I get totals for more than one column in a list and put this into an object using LINQ?

2 Answers2