Question

Problem: Looking to select 1 row of each type

Table: EntryPrices

AttendingTypesId (int)

Name (nvarchar)

Price (int)

GroupId (int)

FromDate (DateTime) //yyyy-MM-dd

Sample:
Basic entry – 100 – 1 – 2012-08-01

Sponsor entry – 350 – 2 – 2012-08-01

Staff entry – 70 – 3 – 2012-08-01

Basic entry – 150 – 1 – 2012-10-01

Basic entry – 200 – 1 – 2012-12-01

As you can see, there are 3 basic entries. Each is valid depending on the date when they registered.
So if a person registers in mid september, he gets it for 100
mid November 150 and end December 200.

However i want to get the “valid” fee depending on todays date and i want to list that in a dropdown list.

So if i query this today (2012-aug-02) i should get the following
rows:

Basic entry – 100 – 1 – 2012-08-01

Sponsor entry – 350 – 2 – 2012-08-01

Staff entry – 70 – 3 – 2012-08-01

If i query this (2012-dec-20) i should get the following rows:

Sponsor entry – 350 – 2 – 2012-08-01

Staff entry – 70 – 3 – 2012-08-01

Basic entry – 200 – 1 – 2012-12-01

How can i construct this in linq-to-sql?

My idea was something like:

var f = from data in mc.AttendingTypes
                    where DateTime.Now.CompareTo(data.FromDate) > 0
                    group data by new { data.GroupId, data.Name, data.Price, data.AttendingTypesId }
                    into newData
                    select new { newData.Key.Name, newData.Key.Price, newData.Key.AttendingTypesId };

Answer 1

I’d rather do something like that :

var today = DateTime.Now;

var result = mc.AttendingTypes
             .Where(at => at.FromDate <= today)
             .GroupBy(at => at.GroupId)
             .Select(g => g.OrderByDescending(m => m.FromDate).FirstOrDefault())
             .ToList();