C# linq / Lambda - Adding an item to a list that summarizes all the items in the list

Nan fish 0
Viewed 39

I have al list of Purches items

I want to add new item to my list, that sum all the items in my list

this is my code:

    public class Purches
    {
        public int Id { get; set; }
        public int Items { get; set; }
        public int TotalPrice { get; set; }
    }

 List<Purches> purchesList = new List<Purches>() {
        new Purches() {
            Id = 1,
            Items = 3,
            TotalPrice = 220
        },
        new Purches() {
            Id = 2,
            Items = 5,
            TotalPrice = 300
        }
   };

now, I want to add the list new item that sum the Items and the TotalPrice properties

the result will be something like that:

 List<Purches> purchesList = new List<Purches>() {
                new Purches() {
                    Id = 1,
                    Items = 3,
                    TotalPrice = 220
                },
                new Purches()
                {
                    Id = 2,
                    Items = 5,
                    TotalPrice = 300
                },
                new Purches()
                {
                    Id = 0,
                    Items = 8,
                    TotalPrice = 550
                }
            };

I have to do it via linq / Lambda in c#

lambda linq c#
2 Answers
Purches totalSum = new Purches
{
    Id = 0,
    Items = purchesList.Sum(p => p.Items),
    TotalPrices = purchesList.Sum(p => p.TotalPrices)
};
// now add it to your list if desired
Tim Schmelter0

I would not recommend adding a summary item of the same type. That is just likely to lead to confusion. A better solution would be to to use either a separate object for the total, or use different types with a shared interface, for example:

public class PurchaceSummary{
    public List<Purches> Purchases {get;}
    public TotalItemCount => Items.Sum(p => p.Items);
    public TotalPrice => Items.Sum(p => p.TotalPrices);
}

Or

public interface IPurchaseLineItem{
    public int Items { get;  }
    public int TotalPrice { get;  }
}
public interface Purchase : IPurchaseLineItem{
    public int Id { get; set; }
    public int Items { get; set; }
    public int TotalPrice { get; set; }
}
public interface PurchaseSummary : IPurchaseLineItem{
    public int Items { get; set; }
    public int TotalPrice { get; set; }
}
// Use the LINQ methods from the previous example to create your totals for the summary

In either case it should be immediately obvious for everyone what each value represents.

JonasH0
Related