numerator & denominator is squared when I multiply 2 times

Fraction file:

using System;
namespace MathLib.Fraction
{
    public struct Fraction
    {
        // Private Member
        static int prNumer;
        static int prDenom;

        // Constructor
        public Fraction(int _numer, int _denom)
        {
            if(_denom == 0)
            {
                throw new ArgumentException("Denominator cannot be Zero.", "_denom");
            }

            prNumer = _numer;
            prDenom = _denom;
        }

        // Other
        public int GetNumer()
        {
            return prNumer;
        }
        public int GetDenom()
        {
            return prDenom;
        }
        public override string ToString()
        {
            return prNumer + "/" + prDenom;
        }

        // Operator Overloading
        public static Fraction operator *(Fraction left, Fraction right)
        {
            int numer = left.GetNumer() * right.GetNumer();
            int denom = left.GetDenom() * right.GetDenom();

            return new Fraction(numer, denom);
        }
    }
}

Main file:

using System;
using MathLib;
using MathLib.Fraction;

namespace MathLibTest
{
    class Program
    {
        static void Main(string[] args)
        {
            Fraction a = new Fraction(3, 5);
            Fraction b = new Fraction(6, 8);

            Console.WriteLine(a * b); // 36/64
            Console.WriteLine(a * b); // 1296/4096 what I expected is: 36/64 again
        }
    }
}

What I’m trying to accomplish: Just making a simple math library that I will use at future. I’m not joking I’ll use this in the future 🙂

Approach that I tried: Rewriting the entire fraction class, 30 minutes of searching what is wrong and still wrong

// Sorry for my bad english 🙂

>Solution :

        static int prNumer;
        static int prDenom;

Remove the static; static means there is only one value shared over all instances (unless it is [ThreadStatic]). You want a per-instance value, so: remove static.

I would also recommend marking the fields readonly, and using readonly struct if you’re using a recent C# version.

---

Full recommended version, for reference:

public readonly struct Fraction : IEquatable<Fraction>
{
    public int Numerator { get; }
    public int Denominator { get; }

    public Fraction(int numererator, int denominator)
    {
        if (denominator == 0)
        {
            throw new ArgumentException("Denominator cannot be Zero.", nameof(denominator));
        }
        // TODO: lowest common denominator
        Numerator = numererator;
        Denominator = denominator;
    }

    public override string ToString() => $"{Numerator}/{Denominator}";

    public static Fraction operator *(Fraction left, Fraction right)
        => new Fraction(left.Numerator  * right.Numerator, left.Denominator * right.Denominator);

    public override int GetHashCode() => HashCode.Combine(Numerator, Denominator);

    public override bool Equals([NotNullWhen(true)] object obj)
        => obj is Fraction other && Equals(other);
    public bool Equals(Fraction other)
        => Numerator == other.Numerator && Denominator == other.Denominator;
}