LG

namespace ModelViewPresenter
{
    public interface IView
    {
        string TextValue { get; }
    }
}

namespace ModelViewPresenter
{
    public interface IModel
    {
        void Set(string value);
        void Reverse(string value);
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
 
namespace ModelViewPresenter
{
    public class Presenter
    {
        private readonly IView m_View;
        private IModel m_Model;
 
        public Presenter(IView view, IModel model)
        {
            this.m_View = view;
            this.m_Model = model;
        }
 
        public void ReverseTextValue()
        {
            string reversed = ReverseString(m_View.TextValue);
            m_Model.Reverse(reversed);
        }
 
        public void SetTextValue()
        {
            m_Model.Set(m_View.TextValue);
        }
 
        private static string ReverseString(string s)
        {
            char[] arr = s.ToCharArray();
            Array.Reverse(arr);
            return new string(arr);
        }
    }
}

namespace ModelViewPresenter
{
    public partial class Form1 : Form, IView
    {
        private Presenter presenter = null;
        private readonly Model m_Model;
 
        public Form1(Model model)
        {
            m_Model = model;
            InitializeComponent();
            presenter = new Presenter(this, m_Model);
            SubscribeToModelEvents();
        }
 
        public string TextValue
        {
            get
            {
                return textBox1.Text;
            }
        }
 
        private void Set_Click(object sender, EventArgs e)
        {
            presenter.SetTextValue();
        }
 
        private void Reverse_Click(object sender, EventArgs e)
        {
            presenter.ReverseTextValue();
        }
 
        private void SubscribeToModelEvents()
        {
            m_Model.TextSet += m_Model_TextSet;         
        }
 
        void m_Model_TextSet(object sender, CustomArgs e)
        {
            this.textBox1.Text = e.m_after;
            this.label1.Text = "Text changed from " + e.m_before + " to " + e.m_after;
        }
    }
}

namespace ModelViewPresenter
{
    public class Model : IModel
    {
        private string m_textValue;
 
        public event EventHandler<CustomArgs> TextSet;
 
        public Model()
        {
            m_textValue = "";
        }
 
        public void Set(string value)
        {
            string before = m_textValue;
            m_textValue = value;
            RaiseTextSetEvent(before, m_textValue);
        }
 
        public void Reverse(string value)
        {
            string before = m_textValue;
            m_textValue = value;
            RaiseTextSetEvent(m_textValue, before);
        }
 
        public void RaiseTextSetEvent(string before, string after)
        {
            TextSet(this, new CustomArgs(before, after));
        }
    }
 
    public class CustomArgs : EventArgs
    {
        public string m_before { get; set; }
        public string m_after { get; set; }
 
        public CustomArgs(string before, string after)
        {
            m_before = before;
            m_after = after;
        }
    }
}