CODEWITHSUNDEEP
c#linqc#-4.0linq-to-sqllinq-to-entities
DooDoo
DooDoo

Reputation: 13467

OrderByDescending(o => o.X).OrderBy(o => o.Y) does not work properly

Please consider this SQL script:

DECLARE @date DATE
SELECT @date = GETDATE();

DECLARE @tbl TABLE (F1 INT, F2 INT, F3 DATETIME, F4 NVARCHAR(50))

INSERT INTO @tbl(F1,F2,F3,F4)
VALUES(6,0,DATEADD(DAY, -8, @date),'1nima'),
      (21, 78, DATEADD(DAY, -5, @date), '2nima'),
      (58, 1, DATEADD(DAY, 10, @date), 'nima'),
      (6, 56, DATEADD(DAY, 1, @date), 'nima'),
      (0, 21, DATEADD(DAY, 0, @date), '3nima'),
      (13, 78, DATEADD(DAY, -8, @date), '8nima'),
      (8, 0, DATEADD(DAY, -8, @date), '9nima')

SELECT * FROM @tbl ORDER BY F3 DESC,F1 ASC

it returns this result and this is correct:

enter image description here

Now I want write that code using linq orders don't work properly:

var lst = new List<cls>();
    lst.Add(new cls() { F1 = 6, F2 = 0, F3 = DateTime.Today.AddDays(-8), F4 = "1nima" });
    lst.Add(new cls() { F1 = 21, F2 = 78, F3 = DateTime.Today.AddDays(-5), F4 = "2nima" });
    lst.Add(new cls() { F1 = 58, F2 = 1, F3 = DateTime.Today.AddDays(10), F4 = "nima" });
    lst.Add(new cls() { F1 = 6, F2 = 56, F3 = DateTime.Today.AddDays(1), F4 = "nima" });
    lst.Add(new cls() { F1 = 0, F2 = 21, F3 = DateTime.Today.AddDays(0), F4 = "3nima" });
    lst.Add(new cls() { F1 = 13, F2 = 78, F3 = DateTime.Today.AddDays(-8), F4 = "8nima" });
    lst.Add(new cls() { F1 = 8, F2 = 0, F3 = DateTime.Today.AddDays(-8), F4 = "9nima" });

    var orderlist = lst.OrderByDescending(o => o.F3).OrderBy(o => o.F1).ToList();
    GridView1.DataSource = orderlist;
    GridView1.DataBind();

it returns this result but this is wrong order:

enter image description here

Why this two result are not equal?

thanks

Upvotes: 0

Views: 72

Answers (2)

Joachim Isaksson
Joachim Isaksson

Reputation: 180987

In your statement;

lst.OrderByDescending(o => o.F3).OrderBy(o => o.F1).ToList();

...the second OrderBy replaces the sort criteria of the IEnumerable completely (ie replaces OrderByDescending) instead of adding an extra criteria.
What you want is to add an extra secondary sort criteria which is done by ThenBy();

lst.OrderByDescending(o => o.F3).ThenBy(o => o.F1).ToList();

Upvotes: 2

Rangesh
Rangesh

Reputation: 728

Did you Try Then By?

var orderlist = lst.OrderByDescending(o => o.F3).ThenBy(o => o.F1).ToList();

Upvotes: 1

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