CODEWITHSUNDEEP
c#linqentity-framework
wytes
wytes

Reputation: 421

GroupBy and OrderBy using LINQ

I get data from my db using linq. I would like to use a GroupBy and an OrderBy on the same Request.

I actually have this code which doesn't work:

var mydata = _db.table1
    .Join(_db.table2, h => h.col1, t => t.col2, 
        (h, t) => new ActivatedScripts() 
        {
            col1 = h.col1, col2 = h.col2, col3 = (t.col3 == "Y"), col4 = "" 
        })
    .GroupBy(z => z.col1).OrderBy(s => s.....);

the OrderBy(s => s...) suggest me all the LINQ method and a famous KEY which doesn't match any column in my code.

EDIT :

I follow the official tutorial to sort my table (http://www.asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/sorting-filtering-and-paging-with-the-entity-framework-in-an-asp-net-mvc-application).

When I groupBy then sort (I tried to sort then groupby) I have an exception :

enter image description here

Upvotes: 0

Views: 1642

Answers (2)

Andrew Khmylov
Andrew Khmylov

Reputation: 762

You can always order first and then group the ordered data:

.Join(...).OrderBy(x => x.col1).GroupBy(x => x.col2)

Upvotes: 1

Guffa
Guffa

Reputation: 700730

The GroupBy method returns a collection of groups. You can easily sort on the col1 column as that is the Key property of each group:

.OrderBy(s => s.Key)

If you want to sort on anything else, you have to get that value from the items in the group. If you for example know that a value is the same for all items in each group, you can get the value from the first item in the group:

.OrderBy(s => s.First().col2)

You can also use aggregates to calculate values using all the items in the group, for example sorting on the sum of the values:

.OrderBy(s => s.Sum(x => x.col2))

Upvotes: 3

Related Questions