C＃泛型类型有一个构造函数？ [英] C#: Generic types that have a constructor?

问题描述

我有下面的C＃测试代码：

I have the following C# test code:

  class MyItem
  {
    MyItem( int a ) {}
  }

  class MyContainer< T >
    where T : MyItem, new()
  {
    public void CreateItem()
    {
      T oItem = new T( 10 );
    }
  }

Visual Studio中无法编译，错误的是在行，其中新的方法有：

Visual Studio can't compile it, the error is at line where 'new' is used:

'T': cannot provide arguments when creating an instance of a variable type

是否有可能在C＃创建泛型类型与非参数构造函数的对象？这是没有问题，做这种事在C ++模板，所以我很好奇，为什么我不能做同样的事情在C＃。也许一些额外的在那里要求或语法是不同的。

Is it possible in C# to create an object of generic type with non-parameterless constructor? It's no problem to do such thing in C++ templates, so i'm very curious why i can't do same thing in C#. Maybe some additional 'where' is required or syntax is different?

推荐答案

它可以与反思做？

public void CreateItem()
{
  int constructorparm1 = 10;
  T oItem = Activator.CreateInstance(typeof(T), constructorparm1) as T;
}

但是有没有通用的约束，以确保 T 实现所需的构造，所以，除非你很小心声明在每一个实现该接口类型构造我不建议这样做。

But there is no generic constraint to ensure that T implements the desired constructor, so I wouldn't advise doing this unless you are careful to declare that constructor in every type that implements the interface.

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