自动INotifyPropertyChanged

Question

是否有任何方法可以在不需要在每个设置器中编写OnPropertyChanged的情况下自动获得类中属性更改的通知？(我有数以百计的财产，我想知道它们是否发生了变化)。

安东建议动态代理。实际上，我在过去使用过类似的“城堡”库，虽然它确实减少了我必须编写的代码量，但它为我的程序启动时间(ymmv)增加了大约30秒--因为它是一个运行时解决方案。

我想知道是否有编译时解决方案，也许使用编译时属性.

Slashene和TcKs给出了生成重复代码的建议--不幸的是，并不是我所有的属性都是m_Value = value的简单例子--它们中很多都有自定义代码，所以代码片段和xml中的cookie裁剪代码对我的项目也不太可行。

Answer 1

2015年7月，在C# 6.0和.NET 4.6以及VS2015中实施了名操作人员的名称。对于C# < 6.0，以下内容仍然有效

我们使用下面的代码(来自http://www.ingebrigtsen.info/post/2008/12/11/INotifyPropertyChanged-revisited.aspx)。伟大的作品:)

public static class NotificationExtensions
{
    #region Delegates

    /// <summary>
    /// A property changed handler without the property name.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="sender">The object that raised the event.</param>
    public delegate void PropertyChangedHandler<TSender>(TSender sender);

    #endregion

    /// <summary>
    /// Notifies listeners about a change.
    /// </summary>
    /// <param name="EventHandler">The event to raise.</param>
    /// <param name="Property">The property that changed.</param>
    public static void Notify(this PropertyChangedEventHandler EventHandler, Expression<Func<object>> Property)
    {
        // Check for null
        if (EventHandler == null)
            return;

        // Get property name
        var lambda = Property as LambdaExpression;
        MemberExpression memberExpression;
        if (lambda.Body is UnaryExpression)
        {
            var unaryExpression = lambda.Body as UnaryExpression;
            memberExpression = unaryExpression.Operand as MemberExpression;
        }
        else
        {
            memberExpression = lambda.Body as MemberExpression;
        }

        ConstantExpression constantExpression;
        if (memberExpression.Expression is UnaryExpression)
        {
            var unaryExpression = memberExpression.Expression as UnaryExpression;
            constantExpression = unaryExpression.Operand as ConstantExpression;
        }
        else
        {
            constantExpression = memberExpression.Expression as ConstantExpression;
        }

        var propertyInfo = memberExpression.Member as PropertyInfo;

        // Invoke event
        foreach (Delegate del in EventHandler.GetInvocationList())
        {
            del.DynamicInvoke(new[]
            {
                constantExpression.Value, new PropertyChangedEventArgs(propertyInfo.Name)
            });
        }
    }


    /// <summary>
    /// Subscribe to changes in an object implementing INotifiyPropertyChanged.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="ObjectThatNotifies">The object you are interested in.</param>
    /// <param name="Property">The property you are interested in.</param>
    /// <param name="Handler">The delegate that will handle the event.</param>
    public static void SubscribeToChange<T>(this T ObjectThatNotifies, Expression<Func<object>> Property, PropertyChangedHandler<T> Handler) where T : INotifyPropertyChanged
    {
        // Add a new PropertyChangedEventHandler
        ObjectThatNotifies.PropertyChanged += (s, e) =>
            {
                // Get name of Property
                var lambda = Property as LambdaExpression;
                MemberExpression memberExpression;
                if (lambda.Body is UnaryExpression)
                {
                    var unaryExpression = lambda.Body as UnaryExpression;
                    memberExpression = unaryExpression.Operand as MemberExpression;
                }
                else
                {
                    memberExpression = lambda.Body as MemberExpression;
                }
                var propertyInfo = memberExpression.Member as PropertyInfo;

                // Notify handler if PropertyName is the one we were interested in
                if (e.PropertyName.Equals(propertyInfo.Name))
                {
                    Handler(ObjectThatNotifies);
                }
            };
    }
}

例如，用这种方式：

public class Employee : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    private string _firstName;
    public string FirstName
    {
        get { return this._firstName; }
        set
        {
            this._firstName = value;
            this.PropertyChanged.Notify(()=>this.FirstName);
        }
    }
}

private void firstName_PropertyChanged(Employee sender)
{
    Console.WriteLine(sender.FirstName);
}

employee = new Employee();
employee.SubscribeToChange(() => employee.FirstName, firstName_PropertyChanged);

该示例中可能存在一些语法错误。没试过。但你至少应该有这样的概念:)

编辑：，我现在看到你想要的工作可能更少了，但是是的.上面的东西至少让事情变得简单多了。还可以防止使用字符串引用属性时出现的所有可怕问题。

Answer 2

Framework4.5为我们提供了CallerMemberNameAttribute，因此不必将属性名称作为字符串传递：

private string m_myProperty;
public string MyProperty
{
    get { return m_myProperty; }
    set
    {
        m_myProperty = value;
        OnPropertyChanged();
    }
}

private void OnPropertyChanged([CallerMemberName] string propertyName = "none passed")
{
    // ... do stuff here ...
}

类似于Svish的解决方案，只需用无聊的框架功能替换lambda awesomeness；)

如果您正在使用安装了KB2468871的Framework4.0，您可以通过努基特安装Microsoft兼容性包，这也提供了这个属性。

Answer 3

实现类型安全的INotifyPropertyChanged：看这里

然后制作您自己的代码片段：

private $Type$ _$PropertyName$;
public $Type$ $PropertyName$
{
    get
    {
        return _$PropertyName$;
    }
    set
    {
        if(value != _$PropertyName$)
        {
            _$PropertyName$ = value;
            OnPropertyChanged(o => o.$PropertyName$);               
        }
    }
}

与代码片段设计器和你已经做了！构建INotifyPropertyChanged的简单、安全的方法。