Group by in LINQ C#

Question

I have a scenario where I am getting a data table with the following values:

 UserId   DeptId deptname  DependentName
  1          45     test       test1
  1          45     test       test2
  1          45     test       test3
  2          46     y          firstName
  2          46     y          firstName1
  2          46     y          firstName2

I need a LINQ query where I need to get one to get in the following format:

user id = 1
deptid = 45 
deptname = test

DependentName = {test1,tes2,test3}

user id = 2
deptid = 46 
deptname = y

DependentName = {firstName,firstName1,firstName2}

So, you want to get `DependentName` as a comma separated string. Am i right? — Maciej Los, Jun 09 '16 at 18:57
I bet he didn't even try. if he google linq101, he would've gotten the answer. — dfdsfdsfsdf, Jun 09 '16 at 18:59
FYI..i tried and then came to help site but the value for dependent is not grouping and still trying it. Thanks for your time. — user3334074, Jun 09 '16 at 19:07

score 0 · Accepted Answer · answered Jun 09 '16 at 18:58

0

What is a problem?

var result = ctx.Entity.GroupBy(u => new { 
   u.UserId,
   u.DeptId,
   u.DeptName
}).ToList().Select(grouped => new { 
    GroupKey = grouped.Key,
    DeptNames => string.Join(",", grouped.Select(gr => gr.DependentName)) 
});

answered Jun 09 '16 at 18:58

pwas

3,225
18
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1

`ToList()` after `GroupBy` is redundant! – Maciej Los Jun 09 '16 at 18:59
@MaciejLos No. If it is Entity Framework context, `string.Join` will fail without `ToList()`. – pwas Jun 09 '16 at 19:00
I am using datatable as enumerable hence i am failing to get it – user3334074 Jun 09 '16 at 19:01
1

Instead of `ToList` you can use `AsEnumerable`. – juharr Jun 09 '16 at 19:03
Thank you, solved the issue i missed to select the resultset from grouped items. Thanks once again – user3334074 Jun 09 '16 at 20:35

score 0 · Answer 2 · edited May 23 '17 at 12:32

Based on MSDN :

public static IEnumerable<IGrouping<TKey, TElement>> GroupBy<TSource, TKey, TElement>(
    this IEnumerable<TSource> source,
    Func<TSource, TKey> keySelector,
    Func<TSource, TElement> elementSelector
)

This should look like this :

melist.GroupBy(e = > new { e.UserId, e.DeptId, e.Deptname }, e);

This question was already answered here: C# Linq Group By on multiple columns

Group by in LINQ C#

2 Answers2