[CallerMemberName]-based implementation of INotifyPropertyChanged

ObservableObject.cs

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

public abstract class ObservableObject : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected ObservableObject()
    {
        this.properties = new Dictionary<string, object>();
    }
    
    protected object GetValue<T>([CallerMemberName] string propertyName = null)
    {
        return GetProperty(default(T), propertyName);
    }

    protected object GetProperty<T>(T orDefault, [CallerMemberName] string propertyName = null)
    {
        object value;
        return properties.TryGetValue(propertyName, out value) ? (T)value : orDefault;
    }

    protected void SetProperty(object value, [CallerMemberName] string propertyName = null)
    {
        object oldValue;
        bool changed = !(properties.TryGetValue(propertyName, out oldValue) && object.Equals(value, oldValue));
        properties[propertyName] = value;
        if (changed)
        {
            RaisePropertyChanged(propertyName);
        }
    }

    private void RaisePropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = Interlocked.CompareExchange(ref PropertyChanged, null, null);
        if (handler != null)
        {
            handler.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    
    private readonly Dictionary<string, object> properties;
}

namespace Example
{
    public sealed class ExampleViewModel : ObservableObject
    {
        public string UserName
        {
            get { return GetProperty<string>(); }
            set { SetProperty(value);           }
        }

        public int Reputation
        {
            get { return GetProperty<int>(orDefault: 1); }
            set { SetProperty(value);                    }
        }
    }
}