Linq query to count and group items by date

Question

I have a collection of Orders which are pulled from EF. Each Order has an order date:

public class Order {
    public DateTime Date { get; set; }
    public int Id { get; set; }
}

I want to be able to run a query to return the number of orders for each day in a certain date range. The query method should look something like:

public class ICollection<OrderDateSummary> GetOrderTotalsForDateRange(DateTime startDate, DateTime endDate) {

      var orderDateSummary = Set.SelectMany(u => u.Orders) // ..... grouping/totalling here?!

      return orderDateSummary;
}

For info, Set is actually part of a repository which returns a User aggregate root, so the type of Set is DbSet<User> The bit I am stuck on is grouping and totalling the Orders queryable from the SelectMany method.

The OrderDateSummary class looks like:

public OrderDateSummary {
      DateTime Date { get; set; }
      int Total { get; set; }
}

So, the output for a start date of 01/01/2016 and an end date of 03/01/2016 would look something like:

Date          Total
===================
01/01/2016       10
02/01/2016        2
03/01/2016        0
04/01/2016       12

Answer 1

var startDate = new DateTime (2016, 1, 1);
var endDate = new DateTime (2016, 1, 4);

Set.SelectMany(u => u.Orders).
    Where (order => startDate <= order.Date && order.Date <= endDate) // If filter needed
    GroupBy (order => order.Date, (date, values) =>
        new OrderDateSummary () {
            Date = date,
            Total = values.Count ()
        }).
    OrderBy (summary => summary.Date).
    ToList ();

Just you should mark your OrderDateSummary with class or struct and make those properties public or add constructor.

And you have a date 04/01/2016 in expected result, so, I guess, your end time is 4th and not 3th.

Answer 2

how about

List<OrderDateSummary> Result = OrderList       
    .Where(x => x.Date >= startDate && x.Date <= endDate)
    .GroupBy(x => x.Date)
    .Select(z => new OrderDateSummary(){
          Date = z.Key, 
          Total = z.Count()
     }).OrderBy(d=> d.Date).ToList();

Answer 3

As I can see you need to generate all dates in range from start to end . Then calculate total number of orders on each date.

DateTime start = new DateTime(2016, 1, 1);
DateTime end = new DateTime(2016, 1, 4);
Enumerable
    .Range(0, 1 + (end - start).Days)
    .Select(x => start.AddDays(x))
    .GroupJoin(Set.SelectMany(u => u.Orders),
        dt => dt, o => o.Date.Date,
        (dt, orders) => new OrderDateSummary { Date = dt, Total = orders.Count() })
    .ToList();

Check out working example on Ideone .

Answer 4

Try code below which is linq

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;

namespace ConsoleApplication82
{
    class Program
    {
        static void Main(string[] args)
        {
            List<OrderDateSummary> orderSummary = null;

            DataTable dt = new DataTable();
            dt.Columns.Add("id", typeof(int));
            dt.Columns.Add("date", typeof(DateTime));
            dt.Columns.Add("amount", typeof(decimal));

            dt.Rows.Add(new object[] { 1, DateTime.Parse("1/1/16"), 1.00 });
            dt.Rows.Add(new object[] { 2, DateTime.Parse("1/1/16"), 2.00 });
            dt.Rows.Add(new object[] { 3, DateTime.Parse("1/2/16"), 3.00 });
            dt.Rows.Add(new object[] { 4, DateTime.Parse("1/2/16"), 4.00 });
            dt.Rows.Add(new object[] { 5, DateTime.Parse("1/2/16"), 5.00 });
            dt.Rows.Add(new object[] { 6, DateTime.Parse("1/3/16"), 6.00 });
            dt.Rows.Add(new object[] { 7, DateTime.Parse("1/3/16"), 7.00 });

            orderSummary = dt.AsEnumerable()
                .GroupBy(x => x.Field<DateTime>("date"))
                .Select(x => new OrderDateSummary() { Date = x.Key, Total = x.Count() })
                .ToList();
        }

    }
    public class OrderDateSummary {
      public DateTime Date { get; set; }
      public int Total { get; set; }
    }
}