为什么泛型会减少装箱/拆箱操作

Question

From here

// The .NET Framework 2.0 way to create a list
List<int> list1 = new List<int>();

// No boxing, no casting:
list1.Add(3);    

I understand there is no casting. But why no boxing happens?

"3" is on stack and list is in heap.

How it happens that value from stack moved to heap without boxing?

What happens under the hood?

Answer 1

Boxing doesn't happen here because the array that backs the List is T[] , not object[] . Therefore, the runtime knows your items are integers and doesn't need to box them.

Answer 2

List在堆上已经有一个预先分配的int数组，因此只需要将其中一个int更改为3。