DelegateSample.cs

using System;
namespace ConsoleApp2
{
    public class DelegateSample
    {
        public event Action<int>Fn;
        public void Run()
        {
            var a = new VmSample(this);
            a.Start();
            Fn?.Invoke(10);
            a.Stop();
        }
    }

    class VmSample
    {
        private readonly DelegateSample _sample;
        public VmSample(DelegateSample sample)
        {
            _sample = sample;
        }

        public void Start()
        {
            _sample.Fn += Method1;
        }
        
        public void Stop()
        {
            _sample.Fn -= Method1;
        }

        private void Method1(int a)
        {
            Method2(a * 2);
        }

        private void Method2(int x)
        {
            Console.WriteLine($"Method2 x={x}");
        }
    }
}