为什么在.NET中布尔值为4个字节？ [英] Why is a boolean 4 bytes in .NET?
问题描述
为什么System.Boolean占用4个字节？它只存储一个状态，即 true 或 false ，可以将其存储在小于4个字节的空间中。
Why does a System.Boolean take 4 bytes? It just stores one state, either true or false, which could be stored in less space than 4 bytes.
推荐答案
bool 实际上只有1个字节，但是对齐可能导致4个字节在32位平台上使用，甚至在64位平台上为8个字节。例如， Nullable< bool> （又名 bool？）类型使用完整的32位或64位，具体取决于平台-即使仅由两个 bool 组成。 编辑：正如乔恩·斯凯特（Jon Skeet）指出的那样，总是不存在用于对齐的填充。例如， Nullable< bool> s的数组每个对象仅占用2个字节，而不是4或8个字节。
A bool is actually only 1 byte, but alignment may cause 4 bytes to be used on a 32-bit platform, or even 8 bytes on a 64-bit platform. For example, the Nullable<bool> (aka bool?) type uses a full 32 or 64 bits—depending on platform—even though it's comprised of just two bools. EDIT: As pointed out by Jon Skeet, padding for alignment isn't always present. As an example, an array of Nullable<bool>s takes only 2 bytes per object instead of 4 or 8.
但是如果要存储很多 bool 作为成员，（或使用很多 Nullable<> 类型），类的和用户可能会创建它的许多实例，您可以考虑使用 BitVector32 来代替。框架本身使用这种技术来减少许多Windows窗体控件的内存占用。
But even 8 bits to represent a bool can be considered wasteful if you have many of them to store. For this reason, if you create a type that has many bools as members, (or uses many Nullable<> types), and users of your class might create many instances of it, you might consider using a BitVector32 instead. The framework itself uses this technique to reduce the memory footprint of many of the Windows Forms controls, for instance.
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