看着这个标题很复杂,大叔把它拆开说一下,实体属性-变更-追踪器,把它拆成三部分大家看起来就容易懂一些了,实体属性:领域实体里有自己的属性,属性有getter,setter块,用来返回和设置属性的内容;变更:当前属性为赋值时,我们对它进行监视;追踪器:对变量的内容进行处理。好了，我们回到Lind.DDD框架中，在框架里有领域实体基类EntityBase，这个类是所有实体的基类，它公开了一些属性和方法，我们对这个基类进行一些设置，让所有子类都继承它，享用它。
1 属性变更追踪接口和它的事件
// 摘要:
// 向客户端发出某一属性值已更改的通知。
public interface INotifyPropertyChanged
{
// 摘要:
// 在更改属性值时发生。
event PropertyChangedEventHandler PropertyChanged;
}
2 基类EntityBase,添加了事件和它的方法，及触发事件的方法
/// <summary>
/// 领域模型，实体模型基类，它可能有多种持久化方式，如DB,File,Redis,Mongodb,XML等
/// Lind.DDD框架的领域模型与数据库实体合二为一
/// </summary>
[PropertyChangedAttribute]
public abstract class EntityBase : ContextBoundObject, IEntity, INotifyPropertyChanged
{
/// <summary>
/// 实体初始化
/// </summary>
public EntityBase()
{
this.Status = Status.Normal;
this.UpdateDateTime = DateTime.Now;
this.CreateDateTime = DateTime.Now;
this.PropertyChanged += EntityBase_PropertyChanged;
}
/// <summary>
/// 建立时间
/// </summary>
[XmlIgnore, DataMember(Order = 3), XmlElement(Order = 3), DisplayName("建立时间"), Column("CreateTime"), Required]
public DateTime CreateDateTime { get; set; }
/// <summary>
/// 更新时间
/// </summary>
[XmlIgnore, DataMember(Order = 2), XmlElement(Order = 2), DisplayName("更新时间"), Column("UpdateTime"), Required]
public DateTime UpdateDateTime { get; set; }
/// <summary>
/// 实体状态
/// </summary>
[XmlIgnore, DataMember(Order = 1), XmlElement(Order = 1), DisplayName("状态"), Required]
public Status Status { get; set; }
/// <summary>
/// 拿到实体验证的结果列表
/// 结果为null或者Enumerable.Count()==0表达验证成功
/// </summary>
/// <returns></returns>
public IEnumerable<RuleViolation> GetRuleViolations()
{
var properties = this.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance).ToArray();
foreach (var i in properties)
{
var attr = i.GetCustomAttributes();
foreach (var a in attr)
{
var val = (a as ValidationAttribute);
if (val != null)
if (!val.IsValid(i.GetValue(this)))
{
yield return new RuleViolation(val.ErrorMessage, i.Name);
}
}
}
}
#region PropertyChangedEventHandler Events
/// <summary>
/// 属性值变更事件
/// </summary>
public event PropertyChangedEventHandler PropertyChanged;
/// <summary>
/// 事件实例
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
void EntityBase_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
Console.WriteLine("属性:{0},值:{1}", e.PropertyName, sender.GetType().GetProperty(e.PropertyName).GetValue(sender));
}
/// <summary>
/// 触发事件,写在每个属性的set块中CallerMemberName特性表示当前块的属性名
/// </summary>
/// <param name="propertyName"></param>
public void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
}
3 定义变更拦截器特性
/// <summary>
/// 类中方法拦截的特性
/// </summary>
public class PropertyChangedAttribute : ProxyAttribute
{
public override MarshalByRefObject CreateInstance(Type serverType)
{
PropertyChangedProxy realProxy = new PropertyChangedProxy(serverType);
return realProxy.GetTransparentProxy() as MarshalByRefObject;
}
}
4 实现拦截器功能
/// <summary>
/// 属性变更拦截器
/// </summary>
public class PropertyChangedProxy : RealProxy
{
Type serverType;
public PropertyChangedProxy(Type serverType)
: base(serverType)
{
this.serverType = serverType;
}
public override IMessage Invoke(IMessage msg)
{
//构造方法
if (msg is IConstructionCallMessage)
{
IConstructionCallMessage constructCallMsg = msg as IConstructionCallMessage;
IConstructionReturnMessage constructionReturnMessage = this.InitializeServerObject((IConstructionCallMessage)msg);
RealProxy.SetStubData(this, constructionReturnMessage.ReturnValue);
return constructionReturnMessage;
}
//其它方法（属性也是方法,它会被翻译成set_property,get_property,类似于java里的属性封装）
else if (msg is IMethodCallMessage)
{
IMethodCallMessage callMsg = msg as IMethodCallMessage;
object[] args = callMsg.Args;
IMessage message;
try
{
if (callMsg.MethodName.StartsWith("set_") && args.Length == 1)
{
string propertyName = Regex.Split(callMsg.MethodName, "set_")[1];
//这里检测到是set方法，然后应怎么调用对象的其它方法呢？
var method = this.serverType.GetMethod("OnPropertyChanged");
if (method != null)
{
var obj = GetUnwrappedServer();
obj.GetType().GetProperty(propertyName).SetValue(obj, args.FirstOrDefault());
method.Invoke(obj, new object[] { propertyName });//这块对象为空了
}
}
object o = callMsg.MethodBase.Invoke(GetUnwrappedServer(), args);
message = new ReturnMessage(o, args, args.Length, callMsg.LogicalCallContext, callMsg);
}
catch (Exception e)
{
message = new ReturnMessage(e, callMsg);
}
return message;
}
return msg;
}
}
5 总结
本例子主要让大家了解了事件，事件触发机制，AOP拦截技术等知识点，而且通过本例子，我们可以对类的属性进行监视，并订阅一些方法来处理这些变更行为！下面这个代码是最简单的属性变更的记录，本user对象为赋值时，它的两个被set的属性成为了监视的对象
User u1 = new User();
u1.UserName = "OK";
u1.Age = 100;
时间： 2024-08-25 14:21:00