BaseViewModel.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Runtime.CompilerServices;

namespace observingobjects
{
    public class BaseViewModel : INotifyPropertyChanged
    {
        /// <summary>
        /// Sets the property.
        /// </summary>
        /// <returns><c>true</c>, if property was set, <c>false</c> otherwise.</returns>
        /// <param name="backingStore">Backing store.</param>
        /// <param name="value">Value.</param>
        /// <param name="validateValue">Validates value.</param>
        /// <param name="propertyName">Property name.</param>
        /// <param name="onChanged">On changed.</param>
        /// <typeparam name="T">The 1st type parameter.</typeparam>
        protected virtual bool SetProperty<T>(
            ref T backingStore, T value,
            [CallerMemberName]string propertyName = "",
            Action onChanged = null,
            Func<T, T, bool> validateValue = null)
        {
            //if value didn't change
            if (EqualityComparer<T>.Default.Equals(backingStore, value))
                return false;

            //if value changed but didn't validate
            if (validateValue != null && !validateValue(backingStore, value))
                return false;

            backingStore = value;
            onChanged?.Invoke();
            OnPropertyChanged(propertyName);
            return true;
        }


        /// <summary>
        /// Occurs when property changed.
        /// </summary>
        public event PropertyChangedEventHandler PropertyChanged;
        
        /// <summary>
        /// Raises the property changed event.
        /// </summary>
        /// <param name="propertyName">Property name.</param>
        protected virtual void OnPropertyChanged([CallerMemberName]string propertyName = "") =>
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

    }
}