Auto calculate property within class

Question

I have these two classes:

public class LeadPerformanceItem
{
    public string name { get; set; }

    public int visitors { get; set; }

    public decimal visitorspercentoftotal
    {
        get
        {
        // ?
        }
    }
}

public class LeadPerformanceItemCollection
{
    public List<LeadPerformanceItem> items {get;set;}

    public int totalvisitors
    {
        get
        {
            return items.Sum(x => x.visitors);
        }
    }       
}

Is there anyway my visitorspercentoftotal property could be automatically calculated as items are added and removed from the collection?

In order to do that, `LeadPerformanceItem` would need to have access to `List`. Without knowing if it is or is not being collected into a list, how can you expect it to calculate? Instead, you should either give it access to the `List<>`, or just calculate this from the `LeadPerformanceItemCollection` class — Frontear, Apr 29 '19 at 14:08
You can't do it with the build-in `List`, because it is not an observable collection. You could use the [`ObservableCollection`](https://learn.microsoft.com/en-us/dotnet/api/system.collections.objectmodel.observablecollection-1) class, and subscribe to its `CollectionChanged` event. — Theodor Zoulias, Apr 29 '19 at 18:01

Ali Alp · Answer 1 · 2019-04-29T19:45:13.187

  public class LeadPerformanceItem
    {
        public string name { get; set; }

        public int Visitors { get; set; }

        private int _totalVisitors = 0;

        public void UpdateTotalVisitors(int total)
        {
            this._totalVisitors = total;
        }

        public decimal Visitorspercentoftotal => _totalVisitors != 0
            ? Convert.ToDecimal(Math.Round(((double) (Visitors * 100)) / _totalVisitors))
            : 0;
    }

    public class LeadPerformanceItemCollection
    {
        public List<LeadPerformanceItem> Items { get; set; }

        public void AddToItems(LeadPerformanceItem item)
        {
            Items.Add(item);
            var total = Items.Sum(x => x.Visitors);
            Items.AsParallel().ForAll(i => i.UpdateTotalVisitors(total));
        }


        public int totalvisitors
        {
            get { return Items.Sum(x => x.Visitors); }
        }
    }

    [TestFixture]
    public class Class1
    {
        [Test]
        public void Test()
        {
            var leadPerformanceItemCollection = new LeadPerformanceItemCollection();
            leadPerformanceItemCollection.Items=new List<LeadPerformanceItem>();
            leadPerformanceItemCollection.AddToItems(new LeadPerformanceItem()
            {
                name = "test",
                Visitors = 10
            });
            leadPerformanceItemCollection.AddToItems(new LeadPerformanceItem()
            {
                name = "test2",
                Visitors = 25
            });

            Console.WriteLine(leadPerformanceItemCollection.Items[0].Visitorspercentoftotal);
            Console.WriteLine(leadPerformanceItemCollection.Items[1].Visitorspercentoftotal);

        }
    }

result:

29%
71%

score -2 · Answer 2 · answered Apr 29 '19 at 14:21

-2

One way would be to inherit from List and hide the Add method and create your own and do the calculation there.

public class LeadPerformanceItemCollection : List<LeadPerformanceItem>
{

    public new void Add(LeadPerformanceItem item)
    {
        //calculate percent of total here

        base.Add(item);
    }

}

answered Apr 29 '19 at 14:21

Kevin

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Recommended read: https://stackoverflow.com/questions/21692193/why-not-inherit-from-listt?rq=1 – Caramiriel Apr 29 '19 at 14:23

Auto calculate property within class

2 Answers2