Sum on User Defined Types C#

Question

I am trying to do Sum operation on a custom defined type class Percentage

public class Percentage
{
    private readonly decimal pctDecimal; //This has to be private

    public Percentage(decimal decimal_value)
    {
        this.pctDecimal = decimal_value;
    }
}

I am using an Extension method to do the sum

public static class SumExtensions
{
    public static Percentage Sum(this IEnumerable<Percentage> source)
    {
        return source.Aggregate((x, y) =>
        {
            (x + y); //I am getting Error here that "Operator '+' cannot be applied to operand of Type Percentage and Percentage."
        });
    }

}

Any Solution here?

Does this answer your question? [C# Overload generic + operator](https://stackoverflow.com/questions/36307915/c-sharp-overload-generic-operator) — Heretic Monkey, Jan 12 '21 at 16:11
You do realize that summing percentages doesn't really mathematical sense...30/50 -- 60% + 80/100 --> 80% == 110/150 --> 73.3% not 140%. — Charles, Jan 12 '21 at 16:29

score 2 · Accepted Answer · answered Jan 12 '21 at 16:02

2

You need to overload + operator. For example:

public class Percentage
{
    private readonly decimal pctDecimal; //This has to be private

    public Percentage(decimal decimal_value)
    {
        this.pctDecimal = decimal_value;
    }

    public static Percentage operator +(Percentage a, Percentage b)
        => new Percentage(a.pctDecimal + b.pctDecimal);
}

answered Jan 12 '21 at 16:02

Quercus

2,015
1
12
18

is this only going to work on 2 Percentage Objects? any way to extend it to a list of objects? – John Sheedy Jan 12 '21 at 16:19
It works for two objects - `+` is a binary operation. However, now, you can use your `SumExtensions`. – Quercus Jan 12 '21 at 16:21

score 0 · Answer 2 · answered Jan 12 '21 at 16:00

You need to expose your decimal propery

public class Percentage
{
    private readonly decimal pctDecimal;
    public decimal PctDecimal { get {return pctDecimal;} }

    public Percentage(decimal decimal_value)
    {
        this.pctDecimal = decimal_value;
    }
}


public static class SumExtensions
{
    public static Percentage Sum(this IEnumerable<Percentage> source)
    {
        return source.Aggregate((x, y) =>
        {
            (x.PctDecimal  + y.PctDecimal );
        });
    }
}

Sum on User Defined Types C#

2 Answers2