using System;

public class Program

{

    public struct Test : IEquatable<Test>

    {

        public int A { get; }

        public Test(int a)

        {

            A = a;

        }

        public bool Equals(Test other)

        {

            return A == other.A;

        }

        public override bool Equals(object obj)

        {

            return obj is Test other && Equals(other);

        }

        public override int GetHashCode()

        {

            return A.GetHashCode();

        }

        public static bool operator ==(Test a, Test b)

        {

            return a.Equals(b);

        }

        public static bool operator !=(Test a, Test b)

        {

            return !a.Equals(b);

        }

    }

​

    public static void Main()

    {

        var at = new Test(1);

        var bt = new Test(1);

        var ao = (object) at;

        var bo = (object) bt;

        Console.WriteLine(at == bt); // true

        Console.WriteLine(ao == bo); // false

        Console.WriteLine();

        Console.WriteLine(at.Equals(bt)); // true

        Console.WriteLine(ao.Equals(bo)); // true

    }

}