シンプルな計算機のModel

Calculator.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;

namespace MVVMCalculator
{
    public class Calculator : INotifyPropertyChanged
    {

        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChanged(PropertyChangedEventArgs e)
        {
            var propertyChanged = PropertyChanged;
            if (propertyChanged != null)
            {
                propertyChanged(this, e);
            }
        }

        private decimal result;
        public decimal Result
        {
            get
            {
                return this.result;
            }
            protected set
            {
                if (this.result != value)
                {
                    this.result = value;

                    OnPropertyChanged(new PropertyChangedEventArgs("Result"));
                }
            }
        }

        public void Add(decimal value)
        {
            this.Result += value;
        }

        public void Subtract(decimal value)
        {
            this.Result -= value;
        }

        public void Multiply(decimal value)
        {
            this.Result *= value;
        }

        public void Divide(decimal value)
        {
            this.Result /= value;
        }

        public void Clear()
        {
            this.Result = 0m;
        }
    }
}