请问C＃4.0"动态"关键字使泛型多余？ [英] Does the C# 4.0 "dynamic" keyword make Generics redundant?

问题描述

我对C＃中的动态特性（ C＃4动态关键字非常兴奋 - 为什么不），尤其是因为在我的代码库的某些部分我用了很多反思

我的问题是双重的：

1。没有动态代替仿制药，如下面的情况下

泛型方法：

 公共静态无效Do_Something_If_Object_Not_Null< SOMETYPE>（SOMETYPE ObjToTest）{
 
 //测试对象不为空，而无论其类型
如果（EqualityComparer<的！; SOMETYPE> .Default.Equals（ObjToTest，默认（SOMETYPE）））{
 //做些什么
} 
} 
  

动态方法（??）：

 公共静态无效Do_Something_If_Object_Not_Null（动态ObjToTest）{
 
 //测试对象不为空，不管它的类型？但如何？ 
如果（ObjToTest！= NULL）{
 //做些什么
} 
} 
  

2。没有动态现在允许方法返回匿名类型，如下面的情况：

 公共静态清单<动态> ReturnAnonymousType（）{
返回MyDataContext.SomeEntities.Entity.Select（E => e.Property1，e.Property2）.ToList（）; 
} 
  

酷，欢呼声

编辑：

已经通过我的问题想多一点，并在答案的灯光下，我看到我彻底搞砸了主通用/动态问题。他们的确是完全不同的。所以，是的，感谢所有的信息。

约2点，但？

解决方案

动态可能简化反射场景数量有限（你知道成员的名字前面，但没有接口） - 特别是，它可能与一般的运营商帮助（尽管其他的答案存在） - 但比一般的经营诀窍等，很少有。交叉泛型

泛型允许你知道（在编译时）你正在使用的类型 - 相反，动态没有的保养的有关类型。
特别 - 泛型允许您指定并证明了一些关于的一类条件的 - 即它可能实现一些接口或具有公共参数的构造函数。 动态不帮之一：它不支持接口，并且不是简单的不关心的接口糟糕的是，这意味着我们甚至不能查看显式接口实现与动态。

此外，动态真的是对象的一个特例，所以拳击进场，但有vengence。

在现实中，你应该将动态的使用限制在少数情况下：

• COM互操作


• DLR互操作


• 的也许的一些光鸭打字


• 也许的一些通用的运营商

有关所有其他情况下，仿制药和普通C＃是要走的路。

I'm very excited about the dynamic features in C# (C#4 dynamic keyword - why not?), especially because in certain Library parts of my code I use a lot of reflection.

My question is twofold:

1. does "dynamic" replace Generics, as in the case below?

Generics method:

public static void Do_Something_If_Object_Not_Null<SomeType>(SomeType ObjToTest) {

        //test object is not null, regardless of its Type
        if (!EqualityComparer<SomeType>.Default.Equals(ObjToTest, default(SomeType))) {
            //do something
        }
    }

dynamic method(??):

public static void Do_Something_If_Object_Not_Null(dynamic ObjToTest) {

        //test object is not null, regardless of its Type?? but how?
        if (ObjToTest != null) {
            //do something
        }
    }

2. does "dynamic" now allow for methods to return Anonymous types, as in the case below?:

 public static List<dynamic> ReturnAnonymousType() {
        return MyDataContext.SomeEntities.Entity.Select(e => e.Property1, e.Property2).ToList();
    }

cool, cheers

EDIT:

Having thought through my question a little more, and in light of the answers, I see I completely messed up the main generic/dynamic question. They are indeed completely different. So yeah, thanks for all the info.

What about point 2 though?

解决方案

dynamic might simplify a limited number of reflection scenarios (where you know the member-name up front, but there is no interface) - in particular, it might help with generic operators (although other answers exist) - but other than the generic operators trick, there is little crossover with generics.

Generics allow you to know (at compile time) about the type you are working with - conversely, dynamic doesn't care about the type. In particular - generics allow you to specify and prove a number of conditions about a type - i.e. it might implement some interface, or have a public parameterless constructor. dynamic doesn't help with either: it doesn't support interfaces, and worse than simply not caring about interfaces, it means that we can't even see explicit interface implementations with dynamic.

Additionally, dynamic is really a special case of object, so boxing comes into play, but with a vengence.

In reality, you should limit your use of dynamic to a few cases:

• COM interop
• DLR interop
• maybe some light duck typing
• maybe some generic operators

For all other cases, generics and regular C# are the way to go.

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