I need to calculate how many orders there are in total every day and print them in the datatable day by day. I have to perform this time allocation based on the OrderDate value in my table. I need to find the total number of orders for each day.

I want to do:

Order class:

public class Order : IBaseEntity
{
    [Key]
    public int OrderId { get; set; }
    public int UserId { get; set; }
    public int RestaurantId { get; set; }
    public int AddressId { get; set; }

    public int? PromotionId { get; set; }
    public DateTime OrderDate { get; set; }
    public DateTime? DeliveryDate { get; set; }
    public OrderStatues OrderStatus { get; set; }
    public bool DropDoor { get; set; }
    public bool RingBell { get; set; }
    public string OrderNote { get; set; }
    public OrderTypes OrderType { get; set; }
    public string PaymentType { get; set; }
    public decimal SubTotal { get; set; }
    public decimal DiscountTotal { get; set; }
    public decimal OrderTotal { get; set; }
    public decimal DeliveryCost { get; set; }

    public OrderSources OrderSource { get; set; }
    public OrderTimes OrderTime { get; set; }
    public OrderDays OrderDay { get; set; }

    [NotMapped]
    public int[] SelectedProducts { get; set; }

    [NotMapped]
    public int OrderHour { get; set; }

    public virtual Restaurant Restaurant { get; set; }
    public virtual User User { get; set; }
    public virtual Address Address { get; set; }
    public virtual Promotion Promotion { get; set; }

    public virtual ICollection<JoinOrderProduct> JoinOrderProducts { get; set; } = new HashSet<JoinOrderProduct>();

    public void Build(ModelBuilder builder)
    {
        builder.Entity<Order>(entity =>
        {
            entity
            .HasKey(p => new { p.OrderId});

            entity
          .HasOne(p => p.Restaurant)
          .WithMany(p => p.Orders)
          .HasForeignKey(p => p.RestaurantId)
          .OnDelete(DeleteBehavior.Cascade);

            entity
           .Property(p => p.SubTotal)
           .HasPrecision(18, 4)
           .IsRequired();

            entity
           .Property(p => p.DiscountTotal)
           .HasPrecision(18, 4)
           .IsRequired();

            entity
           .Property(p => p.OrderTotal)
           .HasPrecision(18, 4)
           .IsRequired();

            entity
       .Property(p => p.DeliveryCost)
       .HasPrecision(18, 4)
       .IsRequired();

        });
    }
}

CodePudding user response：

I need to find the total number of orders for each day.

I assume that if two Order objects ahave the same value for property Order.OrderDate.Date, that you define them as two orders on the same day.

In this case, you have to group your Orders. Each group consists of Orders that are on one date, = that have the same value for property Order.OrderDate.Date. Once you have these groups, you can count the number of Orders in each group, to know the number of Orders on that date.

For this I use the overload of Enumerable.GroupBy that has a parameter resultSelector. I use the resultSelector to convert the groups into the values that you want.

IEnumerable<Order> orders = ...

// make groups of Orders that have the same order date
var result = orders.GroupBy(order => order.OrderDate.Date,

// parameter resultSelector: use the key (= the common date for all Orders in the group
// and all Orders in the group, to specify the requested output
(commonOrderDate, ordersWithThisDate) => new
{
    Date = commonOrderDate,
    TotalOrder = ordersWithThisDate.Count,
});

In words: from each order in your sequence of Orders, calculate the value of order.OrderDate.Date (= key). Make groups of Orders that have the same key value. For each key-group combination (= common value Orders that have this common value), make one resulting object. This resulting object has two properties:

• Date: the common value of all Orders in the group
• TotalOrder: the number of Orders in this group. This is the number of Orders that were place on this Date.