blocks|key|4540368|text|经过广泛的研究，我能够创建一个解决方案，用于截取同步方法以及异步任务和异步Task<+TResult+>。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4540369|下面是我的异常处理拦截器的代码，它使用Castle动态代理处理所有这些方法类型。此模式适用于执行您希望的任何类型的拦截。对于标准的BeforeInvoke/AfterInvoke操作，语法会更清晰一些，但概念应该是相同的。|4540370|(其他注意事项:示例中的IExceptionHandler接口是自定义类型，而不是通用对象。)|4540371|++++private+class+AsyncExceptionHandlingInterceptor+:+IInterceptor
++++{
++++++++private+static+readonly+MethodInfo+handleAsyncMethodInfo+=+typeof(AsyncExceptionHandlingInterceptor).GetMethod("HandleAsyncWithResult",+BindingFlags.Instance+%7C+BindingFlags.NonPublic);
++++++++private+readonly+IExceptionHandler+_handler;

++++++++public+AsyncExceptionHandlingInterceptor(IExceptionHandler+handler)
++++++++{
++++++++++++_handler+=+handler;
++++++++}

++++++++public+void+Intercept(IInvocation+invocation)
++++++++{
++++++++++++var+delegateType+=+GetDelegateType(invocation);
++++++++++++if+(delegateType+==+MethodType.Synchronous)
++++++++++++{
++++++++++++++++_handler.HandleExceptions(()+=>+invocation.Proceed());
++++++++++++}
++++++++++++if+(delegateType+==+MethodType.AsyncAction)
++++++++++++{
++++++++++++++++invocation.Proceed();
++++++++++++++++invocation.ReturnValue+=+HandleAsync((Task)invocation.ReturnValue);
++++++++++++}
++++++++++++if+(delegateType+==+MethodType.AsyncFunction)
++++++++++++{
++++++++++++++++invocation.Proceed();
++++++++++++++++ExecuteHandleAsyncWithResultUsingReflection(invocation);
++++++++++++}
++++++++}

++++++++private+void+ExecuteHandleAsyncWithResultUsingReflection(IInvocation+invocation)
++++++++{
++++++++++++var+resultType+=+invocation.Method.ReturnType.GetGenericArguments()[0];
++++++++++++var+mi+=+handleAsyncMethodInfo.MakeGenericMethod(resultType);
++++++++++++invocation.ReturnValue+=+mi.Invoke(this,+new[]+{+invocation.ReturnValue+});
++++++++}

++++++++private+async+Task+HandleAsync(Task+task)
++++++++{
++++++++++++await+_handler.HandleExceptions(async+()+=>+await+task);
++++++++}

++++++++private+async+Task<T>+HandleAsyncWithResult<T>(Task<T>+task)
++++++++{
++++++++++++return+await+_handler.HandleExceptions(async+()+=>+await+task);
++++++++}

++++++++private+MethodType+GetDelegateType(IInvocation+invocation)
++++++++{
++++++++++++var+returnType+=+invocation.Method.ReturnType;
++++++++++++if+(returnType+==+typeof(Task))
++++++++++++++++return+MethodType.AsyncAction;
++++++++++++if+(returnType.IsGenericType+&&+returnType.GetGenericTypeDefinition()+==+typeof(Task<>))
++++++++++++++++return+MethodType.AsyncFunction;
++++++++++++return+MethodType.Synchronous;
++++++++}

++++++++private+enum+MethodType
++++++++{
++++++++++++Synchronous,
++++++++++++AsyncAction,
++++++++++++AsyncFunction
++++++++}
++++}|code-block|syntax|javascript|4540372|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|O|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|P|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

After extensive research, I was able to create a solution that works for intercepting Synchronous Methods as well as Async Task and Async Task&lt; TResult >. 

Here is my code for an Exception Handling interceptor that works on all those method types, using Castle Dynamic Proxy. This pattern is adaptable for doing any sort of intercept you wish. The syntax will be a little cleaner for standard BeforeInvoke/AfterInvoke actions, but the concept should be the same. 

(Other note: the IExceptionHandler interface in the example is a custom type, and not a common object.)

<pre><code> private class AsyncExceptionHandlingInterceptor : IInterceptor
 {
 private static readonly MethodInfo handleAsyncMethodInfo = typeof(AsyncExceptionHandlingInterceptor).GetMethod("HandleAsyncWithResult", BindingFlags.Instance | BindingFlags.NonPublic);
 private readonly IExceptionHandler _handler;

 public AsyncExceptionHandlingInterceptor(IExceptionHandler handler)
 {
 _handler = handler;
 }

 public void Intercept(IInvocation invocation)
 {
 var delegateType = GetDelegateType(invocation);
 if (delegateType == MethodType.Synchronous)
 {
 _handler.HandleExceptions(() =&gt; invocation.Proceed());
 }
 if (delegateType == MethodType.AsyncAction)
 {
 invocation.Proceed();
 invocation.ReturnValue = HandleAsync((Task)invocation.ReturnValue);
 }
 if (delegateType == MethodType.AsyncFunction)
 {
 invocation.Proceed();
 ExecuteHandleAsyncWithResultUsingReflection(invocation);
 }
 }

 private void ExecuteHandleAsyncWithResultUsingReflection(IInvocation invocation)
 {
 var resultType = invocation.Method.ReturnType.GetGenericArguments()[0];
 var mi = handleAsyncMethodInfo.MakeGenericMethod(resultType);
 invocation.ReturnValue = mi.Invoke(this, new[] { invocation.ReturnValue });
 }

 private async Task HandleAsync(Task task)
 {
 await _handler.HandleExceptions(async () =&gt; await task);
 }

 private async Task&lt;T&gt; HandleAsyncWithResult&lt;T&gt;(Task&lt;T&gt; task)
 {
 return await _handler.HandleExceptions(async () =&gt; await task);
 }

 private MethodType GetDelegateType(IInvocation invocation)
 {
 var returnType = invocation.Method.ReturnType;
 if (returnType == typeof(Task))
 return MethodType.AsyncAction;
 if (returnType.IsGenericType &amp;&amp; returnType.GetGenericTypeDefinition() == typeof(Task&lt;&gt;))
 return MethodType.AsyncFunction;
 return MethodType.Synchronous;
 }

 private enum MethodType
 {
 Synchronous,
 AsyncAction,
 AsyncFunction
 }
 }
</code></pre>

blocks|key|33157|text|更好的解决方案是使用dynamic关键字绕过编译器类型检查，并在运行时解析操作：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|33158|public+void+Intercept(IInvocation+invocation)
{
++++invocation.Proceed();
++++var+method+=+invocation.MethodInvocationTarget;
++++var+isAsync+=+method.GetCustomAttribute(typeof(AsyncStateMachineAttribute))+!=+null;
++++if+(isAsync+&&+typeof(Task).IsAssignableFrom(method.ReturnType))
++++{
++++++++invocation.ReturnValue+=+InterceptAsync((dynamic)invocation.ReturnValue);
++++}
}

private+static+async+Task+InterceptAsync(Task+task)
{
++++await+task.ConfigureAwait(false);
++++//+do+the+continuation+work+for+Task...
}

private+static+async+Task<T>+InterceptAsync<T>(Task<T>+task)
{
++++T+result+=+await+task.ConfigureAwait(false);
++++//+do+the+continuation+work+for+Task<T>...
++++return+result;
}|code-block|syntax|javascript|33159|entityMap^0|A|7|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

A better solution would be to use the <code>dynamic</code> keyword to bypass the compiler type checking and resolve the operation at run time:

<pre><code>public void Intercept(IInvocation invocation)
{
 invocation.Proceed();
 var method = invocation.MethodInvocationTarget;
 var isAsync = method.GetCustomAttribute(typeof(AsyncStateMachineAttribute)) != null;
 if (isAsync &amp;&amp; typeof(Task).IsAssignableFrom(method.ReturnType))
 {
 invocation.ReturnValue = InterceptAsync((dynamic)invocation.ReturnValue);
 }
}

private static async Task InterceptAsync(Task task)
{
 await task.ConfigureAwait(false);
 // do the continuation work for Task...
}

private static async Task&lt;T&gt; InterceptAsync&lt;T&gt;(Task&lt;T&gt; task)
{
 T result = await task.ConfigureAwait(false);
 // do the continuation work for Task&lt;T&gt;...
 return result;
}
</code></pre>

blocks|key|4540462|text|由于需要拦截返回Task<TResult>的方法，我创建了一个Castle.Core扩展来简化这个过程。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4540463|Castle.Core.AsyncInterceptor|4540464|该程序包可从NuGet下载。|4540465|该解决方案在很大程度上基于@silas-reinagel的回答，但通过提供实现IAsyncInterceptor的新接口简化了该解决方案。还有更多的抽象，使得拦截类似于实现Interceptor。|4540466|有关更多详细信息，请参阅项目的readme。|4540467|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/JSkimming/Castle.Core.AsyncInterceptor|1|https://www.nuget.org/packages/Castle.Core.AsyncInterceptor|2|https://stackoverflow.com/users/4009517/silas-reinagel|3|https://github.com/JSkimming/Castle.Core.AsyncInterceptor#option-1--implement-iasyncinterceptor-interface-to-intercept-invocations|4|https://github.com/JSkimming/Castle.Core.AsyncInterceptor#castlecoreasyncinterceptor^0|8|D|V|B|0|0|S|0|0|6|5|1|0|2E|B|D|F|2|13|H|3|0|F|6|4|0^^$0|@$1|2|3|4|5|6|7|13|8|@$9|14|A|15|B|C]|$9|16|A|17|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|18|8|@]|D|@$9|19|A|1A|1|1B]]|E|$]]|$1|H|3|I|5|6|7|1C|8|@]|D|@$9|1D|A|1E|1|1F]]|E|$]]|$1|J|3|K|5|6|7|1G|8|@$9|1H|A|1I|B|C]]|D|@$9|1J|A|1K|1|1L]|$9|1M|A|1N|1|1O]]|E|$]]|$1|L|3|M|5|6|7|1P|8|@]|D|@$9|1Q|A|1R|1|1S]]|E|$]]|$1|N|3|-4|5|6|7|1T|8|@]|D|@]|E|$]]]|O|$P|$5|Q|R|S|E|$T|U]]|V|$5|Q|R|S|E|$T|W]]|X|$5|Q|R|S|E|$T|Y]]|Z|$5|Q|R|S|E|$T|10]]|11|$5|Q|R|S|E|$T|12]]]]

Having a need to intercept methods returning <code>Task&lt;TResult&gt;</code>, I've created an extension to <code>Castle.Core</code> that simplifies the process.

<a href="https://github.com/JSkimming/Castle.Core.AsyncInterceptor" rel="noreferrer">Castle.Core.AsyncInterceptor</a>

The package is available to download on <a href="https://www.nuget.org/packages/Castle.Core.AsyncInterceptor" rel="noreferrer">NuGet</a>.

The solution is largely based on the answer from <a href="https://stackoverflow.com/users/4009517/silas-reinagel">@silas-reinagel</a>, but simplifies it by providing a new interface to implement <a href="https://github.com/JSkimming/Castle.Core.AsyncInterceptor#option-1--implement-iasyncinterceptor-interface-to-intercept-invocations" rel="noreferrer">IAsyncInterceptor</a>. There are also further abstractions to that make interception similar to implementing <code>Interceptor</code>.

See the <a href="https://github.com/JSkimming/Castle.Core.AsyncInterceptor#castlecoreasyncinterceptor" rel="noreferrer">readme</a> of the project for further details.

blocks|key|4540480|text|我已经这样做了：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4540481|invocation.Proceed();+
object+response;
Type+type+=+invocation.ReturnValue?.GetType();
if+(type+!=+null+&&+typeof(Task).IsAssignableFrom(type))
{
++++var+resultProperty+=+type.GetProperty("Result");
++++response+=+resultProperty.GetValue(invocation.ReturnValue);
}|code-block|syntax|javascript|4540482|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I've done this way:

<pre><code>invocation.Proceed(); 
object response;
Type type = invocation.ReturnValue?.GetType();
if (type != null &amp;&amp; typeof(Task).IsAssignableFrom(type))
{
 var resultProperty = type.GetProperty("Result");
 response = resultProperty.GetValue(invocation.ReturnValue);
}
</code></pre>

blocks|key|4540521|text|@Silas+Reinagel和@thepiat000的解决方案对我不起作用，我也没有成功地使用@James+Skimming的Castle.Core.AsyncInterceptor解决方案。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4540522|在我的例子中，我截获了一个返回Task的异步方法，只有在invocation.Proceed()期间没有异常的情况下，它才应该执行“在invocation.Proceed()代码之后”。最后，我使用了@James+Skimming的code+sample，所以这个解决方案只适用于截取返回Task的异步方法，而不适用于Task<TResult>|4540523|public+void+Intercept(IInvocation+invocation)
{
++++_stepPriorInvocation();

++++invocation.Proceed();
++++Func<Task>+continuation+=+async+()+=>
++++{
++++++++await+(Task)invocation.ReturnValue;

++++++++_stepAfterSuccessfulInvocation();
++++};

++++invocation.ReturnValue+=+continuation();

++++void+_stepPriorInvocation()
++++{
++++}

++++void+_stepAfterSuccessfulInvocation()
++++{
++++}
}|code-block|syntax|javascript|4540524|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/JSkimming/Castle.Core.AsyncInterceptor#methods-that-return-task^0|1S|S|0|F|4|S|K|40|4|4F|D|38|B|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|X|8|@$9|Y|A|Z|B|C]|$9|10|A|11|B|C]|$9|12|A|13|B|C]|$9|14|A|15|B|C]]|D|@$9|16|A|17|1|18]]|E|$]]|$1|H|3|I|5|J|7|19|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|1A|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

The solutions from @Silas Reinagel and @thepirat000 didn't work for me, and I was not successful using <code>Castle.Core.AsyncInterceptor</code> solution from @James Skimming. 

In my case, I'm intercepting an async method returning <code>Task</code>, and it should execute "after invocation.Proceed() code" only if there was no exception during the <code>invocation.Proceed()</code>. At the end I used @James Skimming's <a href="https://github.com/JSkimming/Castle.Core.AsyncInterceptor#methods-that-return-task" rel="nofollow noreferrer">code sample</a>, so this solution works only for intercepting async methods returning <code>Task</code> and not <code>Task&lt;TResult&gt;</code>:

<pre class="lang-cs prettyprint-override"><code>public void Intercept(IInvocation invocation)
{
 _stepPriorInvocation();

 invocation.Proceed();
 Func&lt;Task&gt; continuation = async () =&gt;
 {
 await (Task)invocation.ReturnValue;

 _stepAfterSuccessfulInvocation();
 };

 invocation.ReturnValue = continuation();

 void _stepPriorInvocation()
 {
 }

 void _stepAfterSuccessfulInvocation()
 {
 }
}

</code></pre>

My questions is related to this post <a href="https://stackoverflow.com/questions/14288075/intercept-the-call-to-an-async-method-using-dynamicproxy">Intercept the call to an async method using DynamicProxy</a>

I want to implement interceptor that works with async methods that returns <code>Task</code> or <code>Task&lt;T&gt;</code> result. 

I use next code for return <code>ContinueWith</code> result (in order that caller method wait while interceptor finishes work) 

<pre><code>var task = invocation.ReturnValue as Task;
invocation.ReturnValue = task.ContinueWith(c =&gt; 
 { code that should execute after method finish });
</code></pre>

Above code works fine for <code>Task</code> result, but in case of <code>Task&lt;T&gt;</code> result <code>ContinueWith</code> will change return type from <code>Task&lt;T&gt;</code> to <code>Task</code>.
I need to call overloaded method ContinueWith that returns <code>Task&lt;T&gt;</code>, but for this I need to cast <code>invocation.ReturnValue</code> to <code>Task&lt;T&gt;</code>

I didn't find way to cast it dynamically in any way. 
Does anyone know how to make it?

I also tried to call this method via reflection, but parameter is labmda function that can't be passed directly.

Intercept async method that returns generic Task<> via DynamicProxy

编译器

我的问题与这篇文章有关，我想实现拦截器，它与返回Task或Task<T>结果的异步方法一起工作。我使用next代码返回ContinueWith结果(为了让调用者方法在拦截器完成工作时等待)var task = invocation.ReturnValue as Task;invocation.ReturnValue =...

问截取通过DynamicProxy返回泛型Task<>的异步方法
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