CODEWITHSUNDEEP
c#.net
NayLinHtike
NayLinHtike

Reputation: 1

group by name and order by date and each group order by date in linq

I have the following table.
Name Date
A 10/04/2016
A 10/03/2016
A 10/05/2016
B 10/02/2016
B 10/01/2016
B 10/03/2016
C 10/05/2016
C 10/02/2016
C 10/04/2016

I would like to display this
Name Date
B 10/01/2016
B 10/02/2016
B 10/03/2016
C 10/02/2016
C 10/04/2016
C 10/05/2016
A 10/03/2016
A 10/04/2016
A 10/05/2016

How to create a query to get this result.

Upvotes: 0

Views: 2196

Answers (4)

Andriy Tolstoy
Andriy Tolstoy

Reputation: 6090

var elements = new[]
{
    new { Name = "A", Date = DateTime.Parse("10/04/2016") },
    new { Name = "A", Date = DateTime.Parse("10/03/2016") },
    new { Name = "A", Date = DateTime.Parse("10/05/2016") },

    new { Name = "B", Date = DateTime.Parse("10/02/2016") },
    new { Name = "B", Date = DateTime.Parse("10/01/2016") },
    new { Name = "B", Date = DateTime.Parse("10/03/2016") },

    new { Name = "C", Date = DateTime.Parse("10/05/2016") },
    new { Name = "C", Date = DateTime.Parse("10/02/2016") },
    new { Name = "C", Date = DateTime.Parse("10/04/2016") },
};

// LINQ to Objects
elements
    .GroupBy(e => e.Name)                         // grouping by name                
    .Select(group => group.OrderBy(e => e.Date))  // order elements by date      
    .OrderBy(group => group.First().Date)         // order groups by date
    .SelectMany(group => group);                  // compose groups 

// LINQ to Entities
elements
    .GroupBy(e => e.Name)
    .Select(group => group.OrderBy(e => e.Date))
    .OrderBy(group => group.FirstOrDefault().Date)                   
    .AsEnumerable()
    .SelectMany(group => group);

Upvotes: 1

Alex
Alex

Reputation: 11

https://dotnetfiddle.net/0SfhAz

This is the fiddle with the code. For some reason, I can't get the fiddle to write out the values in the list.

I originally did this in LinqPad, and here is the output I got from the code in the fiddle when in LinqPad

  1. B 10/1/2016
  2. B 10/2/2016
  3. B 10/3/2016
  4. C 10/2/2016
  5. C 10/4/2016
  6. C 10/5/2016
  7. A 10/3/2016
  8. A 10/4/2016
  9. A 10/5/2016

I don't know why I can't just do a writeline on the .net fiddle, but it is being difficult. In case the fiddle doesn't work for you, here it the linq query I used for this

var orderedList = originalList.OrderBy(x => x.SomeDate).GroupBy(y => y.Name);

There may be better approaches, but this looked to solve your issue

Upvotes: 0

dotnetspark
dotnetspark

Reputation: 581

It would be great if you provide more information. Such as, the object type containing the data. Is it a custom model or a DataTable? Any how, I will try both.

var result = dataTable.Rows.AsEnumerable().GroupBy(x => x.Name).OrderBy(x => x.Date);

OR

var result = Foo.GroupBy(x => x.Name).OrderBy(x => x.Date);

Upvotes: 0

kashi_rock
kashi_rock

Reputation: 557

You probably do not need groupby but only orderby can fullfil your task:

yourList.OrderBy(l => l.Date).ThenBy(l => l.Name)

Upvotes: 0

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