Add SetValue call to PropertyChangeBase

[mrfichtn]

When added to PropertyChangedBase, the following calls streamlines implementing properties:

    /// <summary>
    /// Sets property value, raising appropriate message
    /// </summary>
    /// <typeparam name="T">Property type</typeparam>
    /// <param name="oldValue">Property to set</param>
    /// <param name="newValue">New property value</param>
    /// <param name="propertyName">Name used when signaling event</param>
    protected bool SetValue<T>(ref T oldValue, T newValue, string propertyName)
    {
        bool changed;
        if (!Equals(oldValue, newValue))
        {
            oldValue = newValue;
            NotifyOfPropertyChange(propertyName);
            changed = true;
        }
        else
        {
            changed = false;
        }
        return changed;
    }

    /// <summary>
    /// Sets property value, refreshing all bindings
    /// </summary>
    /// <typeparam name="T">Property type</typeparam>
    /// <param name="oldValue">Property to set</param>
    /// <param name="newValue">New property value</param>
    protected bool SetValue<T>(ref T oldValue, T newValue)
    {
        bool changed;
        if (!Equals(oldValue, newValue))
        {
            oldValue = newValue;
            Refresh();
            changed = true;
        }
        else
        {
            changed = false;
        }
        return changed;

    }

    /// <summary>
    /// Sets value, raising changes messages for a group of properties
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="oldValue">Property to set</param>
    /// <param name="newValue">New property value</param>
    /// <param name="propertyNames">Properties affected by change in value</param>
    protected bool SetValue<T>(ref T oldValue, T newValue, params string[] propertyNames)
    {
        bool changed;
        if (!Equals(oldValue, newValue))
        {
            oldValue = newValue;
            foreach (var propertyName in propertyNames)
                NotifyOfPropertyChange(propertyName);
            changed = true;
        }
        else
        {
            changed = false;
        }
        return changed;
    }

For example:
#region Contents Property
public string Contents
{
get => _contents;
set => SetValue(ref _contents, value, nameof(Contents);
}
private string _contents;
#endregion

Thanks!

[nigel-sampson]

Considering adding something like to help reduce some boilerplate (though I recommend using something like PropertyChanged.Fody to get rid of backing fields altogether).