如何一般在C＃中实例化一个泛型类？ [英] How to generically instantiate a generic class in C#?
问题描述
也许它非常简单，但我没有使用类型类型并且它是用途。
< > =
Double 或 T = UInt32 ，取决于某个函数的结果，比如 public static Type CheckType（String input）; 在代码中：
类型t = Program.CheckType（someInput）;如果（t == typeof（Double））
列表< Double>或者typeof（UInt32）
，则返回typeof l =新列表< Double>（）;
else
列表< UInt32> l =新列表< UInt32>（）;
我知道上面的代码不会编译，因为我正在让 l 具有两种不同的含义（一个double列表和一个unsigned int列表）所以它会导致我的问题： p>
- 在上面的代码中是否有避免
if的方法？
类似于此：
类型t = Program.CheckType（someInput）;
列表< t> l =新列表< t>（）; //我知道这不会编译...
我的意思是，一般会实例化一个通用名单...
预先感谢您！
编辑：
不是重复的 标记问题，原因只有一个： Double 和 UInt32 不是匿名类型！这里的问题是如何确定某些输入数据的类型（它将是 Type T = typeof例如，Double）或类型T = typeof（UInt32）），因此，基于该输入数据类型创建通用 SampleClass< T> ， T ！
换句话说：在运行时确定一些
类型T ，然后，使用确定的类型 T 实例化一个泛型类型。 PS：我用 List< T> 作为对话框，如下所示： SampleClass< T> 。因为你不知道类型参数，所以你可以在运行时创建一个List实例。
类型t = Program.CheckType（someInput）;
类型listType = typeof（List>）MakeGenericType（t）;
IList list =（IList）Activator.CreateInstance（listType）;
如果您尝试添加不正确类型的对象，您将得到一个异常，所以这种方法比使用像 ArrayList 或 List
Maybe it is pretty simple, but I'm not in use with the type Type and it's uses.
Say I want to create a List<T> either with T=Double or T=UInt32, depending on the result of some function, say public static Type CheckType(String input);
In code:
Type t = Program.CheckType(someInput); // it returns typeof(Double) or typeof(UInt32)
if (t == typeof(Double))
List<Double> l = new List<Double>();
else
List<UInt32> l = new List<UInt32>();
I know the above code won't compile because I'm letting l to have two different meanings (a list of double and a list of unsigned int)... So it leads to my question:
- Is there a way to avoid the
ifin the above code?
Something similar to this:
Type t = Program.CheckType(someInput);
List<t> l = new List<t>(); // I know this won't compile either...
I mean, that would generically instantiate a generic List...
Thank you in advance!
EDIT:
This is NOT a duplicate of the marked question for only one reason: Double and UInt32 are not Anonymous types! The question, here, is how to determine the type of some input data (which will be Type T=typeof(Double) or Type T=typeof(UInt32), for example) and, thus, create a generic SampleClass<T> based on that input data type, T!
In other words: determine some Type T in the runtime and, then, instantiate a generic type with the determined type T. Sorry if I didn't make that clear before...
PS: I used List<T> as an example for SampleClass<T>.
You can't type the list as generic, since you don't know the type parameter, but you can create a List instance at runtime.
Type t = Program.CheckType(someInput);
Type listType = typeof(List<>).MakeGenericType(t);
IList list = (IList) Activator.CreateInstance(listType);
If you try to add an object of the incorrect type, you will get an exception, so this approach has an advantage over using a collection like ArrayList, or List<object>
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