Postsharp获取截获的方法返回类型

Question

如何获取截获方法的返回类型？我正在编写一个方法级别的缓存机制，我想使用postharp来拦截方法调用。但是，我需要能够将存储的对象转换为原始方法类型。

 public override void OnEntry(MethodExecutionArgs InterceptedItem)
    {
        if (_instance==null)
            _instance = new CouchbaseClient();



        string Key = GetCacheKey(InterceptedItem);


        var CacheItem = _instance.Get(Key);

        if (CacheItem != null)
        {
            // The value was found in cache. Don't execute the method. Return immediately.
            //string StringType = (String)_instance.Get(Key+"Type");
            JavaScriptSerializer jss = new JavaScriptSerializer();
            InterceptedItem.ReturnValue = jss.Deserialize<Object>(CacheItem.ToString());
            //Type Type = Type.GetType(StringType);
            InterceptedItem.ReturnValue = (Object)InterceptedItem.ReturnValue;
               // jss.Deserialize(CacheItem.ToString(), Type.GetType(StringType));
            InterceptedItem.FlowBehavior = FlowBehavior.Return;
        }
        else
        {
            // The value was NOT found in cache. Continue with method execution, but store 
            // the cache key so that we don't have to compute it in OnSuccess.
            InterceptedItem.MethodExecutionTag = Key;
        }
    }

Answer 1

而不是使用

InterceptedItem.ReturnValue = jss.Deserialize<Object>(CacheItem.ToString());

您可以使用以下代码来允许在运行时指定对象的类型（在设计时确定泛型类型参数）：

var mthInfo = InterceptedItem.Method as MethodInfo;
if (mthInfo != null)
    InterceptedItem.ReturnValue = jss.Deserialize(CacheItem.ToString(), mthInfo.ReturnType);
else
    InterceptedItem.ReturnValue = null;

您可以使用MethodBase的{​​{1}}属性检索Method对象。但是，由于MethodExecutionArgs也用于没有返回类型的方法（例如，在MethodBase的情况下），您需要将其强制转换为ConstructorInfo以便能够访问返回类型。