使用泛型类型'System.Collections.Generic.List <T>'需要1个类型参数

Question

What does it mean? I used a list of list in ASP.NET MVC and sent them through ViewData of ActionResuls to retrieve it in views.

However, when I change it to list of list, it gives me an error of HttpWebException . When I check it inside the immediate window, it tells me that the error is:

Using the generic type 'System.Collections.Generic.List<T>' requires 1 type arguments

So, what does it mean and what did I do wrong using it?

Answer 1

The List<T> class is a generic type.

In order to use it, you need to provide a type argument.

For example, if you want to have a list of integers, you need to declare it as List<int> , not List .

Answer 2

I guess you wrote something like List<List>> ...
But there is no class named List.. - List has a generic type parameter.
For example - list of lists of integers should be

List<List<int>> listOfLists = .....

For better understanding of C# generics take a look here .

Answer 3

I was able to just use using System.Collections.Generic; to get access to lists.