内存中对象的大小

Question

如果我有一个具有100个都是int32的属性的类，并且已经实例化了100个这些对象，那么即使在设置任何属性之前还是执行某些操作（或全部）保留该空间，直到您第一次真正为前置操作分配值之前？

Answer 1

When an object is created, the memory for all fields is allocated immediately. Note that the size of the object also includes the object header, padding, etc.

Answer 2

You use the memory as soon as you instantiate the object, because int is a value type.

Reference types work a little different. If you were to make the property strings instead of integers, you would still use the ~40,000 bytes, but no more, because at this point your strings are all null-references (null references still reserve the space for the reference). As you start setting values to the strings, then you would start using the space.

Answer 3

Int32 , like all value types, has a default value. (0)

So yes; as soon as you create those Int32 variables, they are taking up memory.

Answer 4

All class-scoped fields are "assigned" following instantiation, unlike locally-scoped variables, which can remain unassigned indefinitely. Thus, value types consume their appropriate size, and references consume the size of a moving pointer, no matter what--when they are scoped at the class level.

Note also that unless the layout is sequential (as in a struct) or explicit, most value types will be padded to at least 32 bits.

It's not always straightforward to predict how much space a null reference will consume, but were they normal pointers, they would consume 4 bytes on x86 platforms and 8 bytes on x64 platforms.