微软应该为INotifyPropertyChanged实现一些时髦的东西,就像在自动属性中,只需要指定{get;设置;通知;} 我认为这样做很有意义。或者做这个手术有什么并发症吗?
我们能在属性中实现类似notify的东西吗。在你的类中实现INotifyPropertyChanged是否有一个优雅的解决方案,或者唯一的方法是在每个属性中引发PropertyChanged事件。
如果不是,我们可以写一些东西来自动生成一段代码来引发PropertyChanged事件?
微软应该为INotifyPropertyChanged实现一些时髦的东西,就像在自动属性中,只需要指定{get;设置;通知;} 我认为这样做很有意义。或者做这个手术有什么并发症吗?
我们能在属性中实现类似notify的东西吗。在你的类中实现INotifyPropertyChanged是否有一个优雅的解决方案,或者唯一的方法是在每个属性中引发PropertyChanged事件。
如果不是,我们可以写一些东西来自动生成一段代码来引发PropertyChanged事件?
当前回答
一个非常类似aop的方法是动态地将INotifyPropertyChanged注入到已经实例化的对象中。你可以使用像Castle DynamicProxy这样的工具来做到这一点。下面有一篇文章解释了这个技巧:
添加INotifyPropertyChanged到现有对象
其他回答
我刚刚发现ActiveSharp - Automatic INotifyPropertyChanged,我还没有使用它,但它看起来不错。
从它的网站上引用…
发送属性更改通知 没有指定属性名为 字符串。
相反,可以这样写属性:
public int Foo
{
get { return _foo; }
set { SetValue(ref _foo, value); } // <-- no property name here
}
注意,不需要将属性的名称作为字符串包含。ActiveSharp可靠而正确地为自己计算出来。它的工作基于这样一个事实,即你的属性实现通过ref传递支持字段(_foo) (ActiveSharp使用“by ref”调用来识别哪个支持字段被传递,并从字段标识属性)。
=>这里我的解决方案具有以下特征
public ResourceStatus Status
{
get { return _status; }
set
{
_status = value;
Notify(Npcea.Status,Npcea.Comments);
}
}
没有refelction 短的符号 业务代码中没有神奇的字符串 PropertyChangedEventArgs在应用程序中的可重用性 在一条语句中通知多个属性的可能性
使用这个
using System;
using System.ComponentModel;
using System.Reflection;
using System.Reflection.Emit;
using System.Runtime.Remoting.Messaging;
using System.Runtime.Remoting.Proxies;
public static class ObservableFactory
{
public static T Create<T>(T target)
{
if (!typeof(T).IsInterface)
throw new ArgumentException("Target should be an interface", "target");
var proxy = new Observable<T>(target);
return (T)proxy.GetTransparentProxy();
}
}
internal class Observable<T> : RealProxy, INotifyPropertyChanged, INotifyPropertyChanging
{
private readonly T target;
internal Observable(T target)
: base(ImplementINotify(typeof(T)))
{
this.target = target;
}
public override IMessage Invoke(IMessage msg)
{
var methodCall = msg as IMethodCallMessage;
if (methodCall != null)
{
return HandleMethodCall(methodCall);
}
return null;
}
public event PropertyChangingEventHandler PropertyChanging;
public event PropertyChangedEventHandler PropertyChanged;
IMessage HandleMethodCall(IMethodCallMessage methodCall)
{
var isPropertySetterCall = methodCall.MethodName.StartsWith("set_");
var propertyName = isPropertySetterCall ? methodCall.MethodName.Substring(4) : null;
if (isPropertySetterCall)
{
OnPropertyChanging(propertyName);
}
try
{
object methodCalltarget = target;
if (methodCall.MethodName == "add_PropertyChanged" || methodCall.MethodName == "remove_PropertyChanged"||
methodCall.MethodName == "add_PropertyChanging" || methodCall.MethodName == "remove_PropertyChanging")
{
methodCalltarget = this;
}
var result = methodCall.MethodBase.Invoke(methodCalltarget, methodCall.InArgs);
if (isPropertySetterCall)
{
OnPropertyChanged(methodCall.MethodName.Substring(4));
}
return new ReturnMessage(result, null, 0, methodCall.LogicalCallContext, methodCall);
}
catch (TargetInvocationException invocationException)
{
var exception = invocationException.InnerException;
return new ReturnMessage(exception, methodCall);
}
}
protected virtual void OnPropertyChanged(string propertyName)
{
var handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
protected virtual void OnPropertyChanging(string propertyName)
{
var handler = PropertyChanging;
if (handler != null) handler(this, new PropertyChangingEventArgs(propertyName));
}
public static Type ImplementINotify(Type objectType)
{
var tempAssemblyName = new AssemblyName(Guid.NewGuid().ToString());
var dynamicAssembly = AppDomain.CurrentDomain.DefineDynamicAssembly(
tempAssemblyName, AssemblyBuilderAccess.RunAndCollect);
var moduleBuilder = dynamicAssembly.DefineDynamicModule(
tempAssemblyName.Name,
tempAssemblyName + ".dll");
var typeBuilder = moduleBuilder.DefineType(
objectType.FullName, TypeAttributes.Public | TypeAttributes.Interface | TypeAttributes.Abstract);
typeBuilder.AddInterfaceImplementation(objectType);
typeBuilder.AddInterfaceImplementation(typeof(INotifyPropertyChanged));
typeBuilder.AddInterfaceImplementation(typeof(INotifyPropertyChanging));
var newType = typeBuilder.CreateType();
return newType;
}
}
}
让我介绍一下我自己的方法,叫做Yappi。 它属于运行时代理|派生类生成器,向现有对象或类型添加新功能,如种姓项目的动态代理。
它允许在基类中实现INotifyPropertyChanged一次,然后以以下风格声明派生类,仍然支持INotifyPropertyChanged用于新属性:
public class Animal:Concept
{
protected Animal(){}
public virtual string Name { get; set; }
public virtual int Age { get; set; }
}
派生类或代理构造的复杂性可以隐藏在下面这行代码后面:
var animal = Concept.Create<Animal>.New();
所有的INotifyPropertyChanged实现工作可以像这样完成:
public class Concept:INotifyPropertyChanged
{
//Hide constructor
protected Concept(){}
public static class Create<TConcept> where TConcept:Concept
{
//Construct derived Type calling PropertyProxy.ConstructType
public static readonly Type Type = PropertyProxy.ConstructType<TConcept, Implementation<TConcept>>(new Type[0], true);
//Create constructing delegate calling Constructor.Compile
public static Func<TConcept> New = Constructor.Compile<Func<TConcept>>(Type);
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(PropertyChangedEventArgs eventArgs)
{
var caller = PropertyChanged;
if(caller!=null)
{
caller(this, eventArgs);
}
}
//define implementation
public class Implementation<TConcept> : DefaultImplementation<TConcept> where TConcept:Concept
{
public override Func<TBaseType, TResult> OverrideGetter<TBaseType, TDeclaringType, TConstructedType, TResult>(PropertyInfo property)
{
return PropertyImplementation<TBaseType, TDeclaringType>.GetGetter<TResult>(property.Name);
}
/// <summary>
/// Overriding property setter implementation.
/// </summary>
/// <typeparam name="TBaseType">Base type for implementation. TBaseType must be TConcept, and inherits all its constraints. Also TBaseType is TDeclaringType.</typeparam>
/// <typeparam name="TDeclaringType">Type, declaring property.</typeparam>
/// <typeparam name="TConstructedType">Constructed type. TConstructedType is TDeclaringType and TBaseType.</typeparam>
/// <typeparam name="TResult">Type of property.</typeparam>
/// <param name="property">PropertyInfo of property.</param>
/// <returns>Delegate, corresponding to property setter implementation.</returns>
public override Action<TBaseType, TResult> OverrideSetter<TBaseType, TDeclaringType, TConstructedType, TResult>(PropertyInfo property)
{
//This code called once for each declared property on derived type's initialization.
//EventArgs instance is shared between all events for each concrete property.
var eventArgs = new PropertyChangedEventArgs(property.Name);
//get delegates for base calls.
Action<TBaseType, TResult> setter = PropertyImplementation<TBaseType, TDeclaringType>.GetSetter<TResult>(property.Name);
Func<TBaseType, TResult> getter = PropertyImplementation<TBaseType, TDeclaringType>.GetGetter<TResult>(property.Name);
var comparer = EqualityComparer<TResult>.Default;
return (pthis, value) =>
{//This code executes each time property setter is called.
if (comparer.Equals(value, getter(pthis))) return;
//base. call
setter(pthis, value);
//Directly accessing Concept's protected method.
pthis.OnPropertyChanged(eventArgs);
};
}
}
}
它对于重构是完全安全的,在类型构造后不使用反射,并且足够快。
我写了一篇文章来帮助你(https://msdn.microsoft.com/magazine/mt736453)。你可以使用SolSoft。DataBinding NuGet包。然后你可以这样写代码:
public class TestViewModel : IRaisePropertyChanged
{
public TestViewModel()
{
this.m_nameProperty = new NotifyProperty<string>(this, nameof(Name), null);
}
private readonly NotifyProperty<string> m_nameProperty;
public string Name
{
get
{
return m_nameProperty.Value;
}
set
{
m_nameProperty.SetValue(value);
}
}
// Plus implement IRaisePropertyChanged (or extend BaseViewModel)
}
好处:
基类是可选的 没有对每个“设定值”进行反思 可以具有依赖于其他属性的属性,并且它们都自动引发适当的事件(本文有一个这样的示例)