为什么VS2010在链接具有动态参数的方法时失败 [英] Why VS2010 Intelissense fails when chaining methods with dynamic args

问题描述

我想要一些解释你们C＃4.0动态的专家。

I would like some explanation of you guys expert in C# 4.0 dynamic.

我有一个流利的生成器类，以帮助配置对象，然后创建它。这个接口有一个方法SetParameters（...）：

I have a fluent builder class to help configure an object before creating it. This interface has a method SetParameters(...):

    public FluentBuilder<TInterface> SetParameters(dynamic parameters)
    {
        _parameters = parameters;
        return this;
    }

我这样做以消耗流畅的界面：

I'm doing this to consume the fluent interface:

                var order = new Order();

                /* Setting up parameters */
                dynamic parameters = new ExpandoObject();
                parameters.Transaction = transactionObj;
                parameters.CurrentPrincipal = Thread.CurrentPrincipal;

                var proxiedOrder = ObjectProxyFactory
                    .Configure<IOrder>(order)
                    .FilterMethods(o => o.InsertOrder())
                    .AddPreDecoration(AppConcerns.JoinSqlTransaction)
                    .AddPreDecoration(AppConcerns.EnterLog)
                    .AddPostDecoration(AppConcerns.ExitLog)
                    .AddPostDecoration(AppConcerns.SecurityCheck)
                    .SetParameters(parameters)
                    .Teste() //this method doesn't exist in the fluent builder
                    .CreateProxy();

                var result = proxiedOrder.InsertOrder();

如上面的代码片段中所说，在流畅接口中不存在称为Teste ，但是intelissense允许在我调用SetParameters之后写任何方法，像返回动态，但是如代码中所示，SetParameters返回不是动态的FluentInterface。

As commented in the above snippet, the method called Teste() doesn't exists in the fluent interface, but intelissense allow write anymethod after I call SetParameters like it returning dynamic, but as you see in code, SetParameters returns FluentInterface that is not dynamic.

上面的代码编译成功在运行时将失败，因为在运行时方法Teste（）将不会在FluentBuilder类中找到。

The code above compiles sucessfully by in runtime will fail because in runtime the method Teste() will not be found in FluentBuilder class.

要在设计时解决这个问题，并获得正确的Intelissense ，我需要将参数转换为ExpandoObject类：

To resolve this problem in design-time, and to get correct Intelissense, I need to cast the parameter to the ExpandoObject class:

                    var proxiedOrder = ObjectProxyFactory
                    .Configure<IOrder>(order)
                    .FilterMethods(o => o.InsertOrder())
                    .AddPreDecoration(AppConcerns.JoinSqlTransaction)
                    .AddPreDecoration(AppConcerns.EnterLog)
                    .AddPostDecoration(AppConcerns.ExitLog)
                    .AddPostDecoration(AppConcerns.SecurityCheck)
                    .SetParameters((ExpandoObject)parameters) //cast to ExpandoObject
                    .Teste() //now intelissense is giving me an "red" error and solution will not compile
                    .CreateProxy();

                var result = proxiedOrder.InsertOrder();

我发现，任何时候我在任何方法链接中传递C＃动态参数，接收动态参数，后续对方法的调用将像返回一个C＃动态对象一样，即使方法的返回类型不是动态的。

I've found that, anytime I pass a C# dynamic parameter in any method chaining, after that method receiving the dynamic parameter, the subsequent calls to methods will behave like returning a C# dynamic object, even if the return type of the method it's not dynamic.

这是一个错误？或者这是预期发生的吗？

Is it a bug ? Or is this expected to happens ?

推荐答案

预期会发生。任何涉及动态参数的方法调用都是动态解析的 - 在执行时间之前无法确定确切的重载，因此返回类型在编译时是未知的，因此被视为 dynamic 。在某些情况下，C＃编译器可以推断更多的信息（例如，如果它是一个静态方法调用），但为了简单，它不。只有涉及动态值的变量中的少数表达式具有非动态类型。 （从内存中，是运算符总是 bool ，并且构造函数总是假定返回正在构造的类型。 ）

It's expected to happen. Any method call involving a dynamic argument is resolved dynamically - the exact overload can't be determined until execution time, so the return type is unknown at compile time, so it's treated as being dynamic. In some cases the C# compiler could infer more information (e.g. if it's a static method call) but for simplicity it doesn't. Only a variable few expressions involving dynamic values have non-dynamic types. (From memory, the is operator is always bool, and a constructor is always assumed to return the type being constructed.)

编辑：我终于找到规范引用。从第7.6.5节：

I've finally found the spec reference. From section 7.6.5:

如果以下至少一项成立，则调用表达式是动态绑定的（§7.2.2）

An invocation-expression is dynamically bound (§7.2.2) if at least one of the following holds:

• 主表达式的编译时类型为动态。


• 可选参数列表的编译时类型为动态，并且primary-expression没有委托类型。

将调用表达式分类为动态类型的值。

In this case the compiler classifies the invocation-expression as a value of type dynamic.

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