Indirect injection in C#

Example of indirect injection in C#.

using System;
using System.Collections.Generic;
using System.Text;

namespace IndirectInjection
{
    class Program
    {
        
        static void Main(string[] args)
        {
            IMaths im = new Maths();
            Console.WriteLine(im.add(3, 2).ToString());
            Console.ReadLine();
        }
    }
    public interface IMaths
    {
        int add(int a, int b);
        int sub(int a, int b);
    }
    public class Maths : IMaths
    {
        public int add(int a, int b)
        {
            return (a + b);
        }
        public int sub(int a, int b)
        {
            return (a - b);
        }
    }
    
}