dotnet核心中的RealProxy？

Question

我正在使用命名空间System.Runtime.Remoting.Proxies和System.Runtime.Remoting.MessagingC#中的AOP.我正在尝试将我的应用程序从.Net Framework 4.6移植到dnxcore/dotnet核心.

Intellisense说,这两个命名空间不适用于我的framework-vesion(netcoreapp1.0/dnxcore50).知道这两个命名空间是否会出现？或者任何想法如何使用RealProxy-class 获得AOP ？

我不想使用第三方库 - 我只想使用.Net提供给我的东西.

Answer 1

看起来RealProxy不会出现在.NET Core/Standard中.在该问题中,Microsoft开发人员建议将DispatchProxy作为替代方案.

此外,一些现有的AOP框架可能已经或将来支持.NET Core(如对问题的评论中所见).

另一种选择是DispatchProxy,它有一个很好的例子:http://www.c-sharpcorner.com/article/aspect-oriented-programming-in-c-sharp-using-dispatchproxy/.

如果我们简化代码,这就是我们得到的:

public class LoggingDecorator<T> : DispatchProxy
{
    private T _decorated;

    protected override object Invoke(MethodInfo targetMethod, object[] args)
    {
        try
        {
            LogBefore(targetMethod, args);

            var result = targetMethod.Invoke(_decorated, args);

            LogAfter(targetMethod, args, result);
            return result;
        }
        catch (Exception ex) when (ex is TargetInvocationException)
        {
            LogException(ex.InnerException ?? ex, targetMethod);
            throw ex.InnerException ?? ex;
        }
    }

    public static T Create(T decorated)
    {
        object proxy = Create<T, LoggingDecorator<T>>();
        ((LoggingDecorator<T>)proxy).SetParameters(decorated);

        return (T)proxy;
    }

    private void SetParameters(T decorated)
    {
        if (decorated == null)
        {
            throw new ArgumentNullException(nameof(decorated));
        }
        _decorated = decorated;
    }

    private void LogException(Exception exception, MethodInfo methodInfo = null)
    {
        Console.WriteLine($"Class {_decorated.GetType().FullName}, Method {methodInfo.Name} threw exception:\n{exception}");
    }

    private void LogAfter(MethodInfo methodInfo, object[] args, object result)
    {
        Console.WriteLine($"Class {_decorated.GetType().FullName}, Method {methodInfo.Name} executed, Output: {result}");
    }

    private void LogBefore(MethodInfo methodInfo, object[] args)
    {
        Console.WriteLine($"Class {_decorated.GetType().FullName}, Method {methodInfo.Name} is executing");
    }
}

因此,如果我们有一个Calculator带有相应接口的示例类(此处未显示):

public class Calculator : ICalculator
{
    public int Add(int a, int b)
    {
        return a + b;
    }
}

我们可以像这样简单地使用它

static void Main(string[] args)
{
    var decoratedCalculator = LoggingDecorator<ICalculator>.Create(new Calculator());
    decoratedCalculator.Add(3, 5);
    Console.ReadKey();
}

Answer 2

您可以使用任一个System.Reflection.DispatchProxy或您自己的简单装饰器实现.检查Wikipedia上的Decorator模式页面以获取实现示例.

目前在.NET Core中,您无法使用构造函数注入DispatchProxy.您必须使用DispatchProxy.Create()工厂方法和属性注入以及要使用的显式强制转换为代理类型.有关更多信息,请查看.NET Core GitHub存储库中的DispachProxyTest.cs.

这是一个简单的通用装饰器的例子,它继承了DispatchProxy:

class GenericDecorator : DispatchProxy
{
    public object Wrapped { get; set; }
    public Action<MethodInfo, object[]> Start { get; set; }
    public Action<MethodInfo, object[], object> End { get; set; }
    protected override object Invoke(MethodInfo targetMethod, object[] args)
    {
        Start?.Invoke(targetMethod, args);
        object result = targetMethod.Invoke(Wrapped, args);
        End?.Invoke(targetMethod, args, result);
        return result;
    }
}

它的用法:

class Program
{
    static void Main(string[] args)
    {
        IEcho toWrap = new EchoImpl();
        IEcho decorator = DispatchProxy.Create<IEcho, GenericDecorator>();
        ((GenericDecorator)decorator).Wrapped = toWrap;
        ((GenericDecorator)decorator).Start = (tm, a) => Console.WriteLine($"{tm.Name}({string.Join(',', a)}) is started");
        ((GenericDecorator)decorator).End = (tm, a, r) => Console.WriteLine($"{tm.Name}({string.Join(',', a)}) is ended with result {r}");
        string result = decorator.Echo("Hello");
    }

    class EchoImpl : IEcho
    {
        public string Echo(string message) => message;
    }

    interface IEcho
    {
        string Echo(string message);
    }
}