CODEWITHSUNDEEP
c#linqgroup-by
RBear
RBear

Reputation: 383

How to use Linq to group every N number of rows

I cannot find a way to make this work and hoping someone has an idea. A simplified example would be having a list of say integers 1-100, i want to group every 3 rows so the result would be 1,2,3 in first group then 4,5,6 in next group etc. I know how to get every nth record but what I need is all the records so I can then aggregate them, using first, last, sum, max, etc.

Thanks!

Upvotes: 25

Views: 21414

Answers (3)

Sudeep
Sudeep

Reputation: 349

How about a simpler approach:

var index = 0;
var grpOf3s = students.GroupBy(x => index++ / 3);

Update: If you are using the Key value of the group item then you will need to convert the group enumerable to a list. Otherwise you will get a different Key every time it is accessed.

var index = 0;
var grpOf3s = students.GroupBy(x => index++ / 3).ToList();

Upvotes: 2

Scott Ivey
Scott Ivey

Reputation: 41568

This example should work for querying non-numeric collections. It projects an index into the object to be grouped, and then removes it again during the grouping. 

var studentQuery2 = students
    .Select((student, index) => new {student, index})
    .GroupBy(g => g.index / 3, i => i.student);

Upvotes: 46

idursun
idursun

Reputation: 6335

var q = Enumerable.Range(0, 100).GroupBy(x => x/3);

Am I missing something?

Upvotes: 31

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