Use LINQ to group multiple columns & split data into several lists

Question

Recently I have a task which need to do as following description, my question is that is LINQ capable to do it?

Say I have a set of data, each consists of three columns: a(int),b(int),c(int)

What I want to do is to group these data by a and b, and for each distinct pair (a,b), store their corresponding c into separate list.

For example: If I have a set of data(a,b,c) {(1,3,5), (2,4,6), (1,3,7), (2,4,8)},

I want to split the data into two separate list, each contains c's value:

List 1 (a=1,b=3) : [5,7]

List 2 (a=2,b=4) : [6,8]

What I have tried is to group / order by the data by (a,b), and got a sorted list of data, I can of course use any loop to iterate the set of data and split them into several list, just wondering if there is a more beautiful solution, like using a single LINQ query?

Any suggetion is pleased! Thanks :)

chomba · Accepted Answer · 2015-06-11 02:05:42Z

1

Try this:

var result = data.GroupBy(x => new { x.a, x.b })
                 .Select(g => Tuple.Create
                 (
                     new List<int> { g.Key.a, g.Key.b }, 
                     new List<int>(g.Select(x => x.c))
                 )).ToList();

Here's the query expression equivalent:

var result = (from x in data
             group x by new { x.a, x.b } into g
             select Tuple.Create(
                 new List<int> { g.Key.a, g.Key.b }, 
                 new List<int>(g.Select(x => x.c)))).ToList();

edited Jun 11, 2015 at 2:05

answered Jun 11, 2015 at 1:31

chomba

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2 Comments

shole Over a year ago

Thanks, it works! Just want to ask, how can I do this in LINQ to entities? i.e. from s in data...

shole Over a year ago

You are amazing, you got 666 rating now :)

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