事件和事件订阅的数据大小是多少？
抱歉，没有时间在事件上尝试 sizeof，但本着增强 google-fu 的精神......
将向具有事件字段的类实例添加多少实际内存大小？
每次订阅事件将使用多少实际内存？
我假设每个事件或订阅都有单个指针，但我只是想确定一下。
考虑这个例子：
public class VertexMovedArgs : EventArgs {
public Vertex theVert;
}
public class Vertex {
// what size does this add to each Vertex?
public event EventHandler<VertexMovedArgs> VertexMovedEvent;
private Vector3 m_pos;
public Vector3 pos {
get { return m_pos; }
set {
if ( value != m_pos ) {
m_pos = value;
EventHandler<VertexMovedArgs> tellEveryoneWeMoved = VertexMovedEvent;
if ( handler != null ) {
VertexMovedArgs args = new VertexMovedArgs( this );
tellEveryoneWeMoved( this, args );
}
}
}
}
}
public class Mesh {
private List<Vertex> m_verts = new List<Vertex>();
public Vertex AddVert() {
Vertex vert = new Vertex();
// what size per-subscription does this add to this Mesh instance (or elsewhere)?
vert.VertexMovedEvent += onVertexMoved;
m_verts.Add( vert );
}
void onVertexMoved( object sender, VertexMovedArgs args ) {
// play the vertex like a violin, etc...
}
}
Apologies for not quite having the time to try sizeof on an event but in the spirit of enhancing google-fu....
What actual memory size will be added to a class instance which has an event field?
What actual memory will be used for each subscription to an event?
I assume single pointers for each event or subscription, but I just want to be sure.
Consider this example:
public class VertexMovedArgs : EventArgs {
public Vertex theVert;
}
public class Vertex {
// what size does this add to each Vertex?
public event EventHandler<VertexMovedArgs> VertexMovedEvent;
private Vector3 m_pos;
public Vector3 pos {
get { return m_pos; }
set {
if ( value != m_pos ) {
m_pos = value;
EventHandler<VertexMovedArgs> tellEveryoneWeMoved = VertexMovedEvent;
if ( handler != null ) {
VertexMovedArgs args = new VertexMovedArgs( this );
tellEveryoneWeMoved( this, args );
}
}
}
}
}
public class Mesh {
private List<Vertex> m_verts = new List<Vertex>();
public Vertex AddVert() {
Vertex vert = new Vertex();
// what size per-subscription does this add to this Mesh instance (or elsewhere)?
vert.VertexMovedEvent += onVertexMoved;
m_verts.Add( vert );
}
void onVertexMoved( object sender, VertexMovedArgs args ) {
// play the vertex like a violin, etc...
}
}
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事件字段只是一个对象引用。
在您将处理程序（委托）放入其中之前，每个类实例只会消耗一个指针大小（4 或 8 字节）。
委托实例有四个指针大小的字段，加上标准的 CLR 对象头。
它们存储：
多播委托（实际上，所有普通委托）再添加两个：
null）_invocationCount（一个IntPtr），针对不同的情况以不同的方式使用 。我正在撰写一篇博客文章，该文章将更详细地解释这些字段
An event field is just an object reference.
Until you put a handler (delegate) in it, it will just consume one pointer-size (4 or 8 bytes) per class instance.
Delegate instance have four pointer-size fields, plus the standard CLR object header.
They store:
Multicast delegates (in practice, all normal delegates) add two more:
nullfor single delegates)_invocationCount(anIntPtr), used in different ways for different kinds of delegatesI'm in the middle of writing a blog post that will explain these fields in greater detail.
事件是一对方法，用于添加和删除订阅（实际上，它是三个方法，但第三个方法通常不用于任何用途）。事件本身不会向对象实例的大小添加任何内容，但添加/删除逻辑通常必须添加至少一个字段。事件最常见的默认实现是创建一个 MultiCastDelegate 类型的字段，并使用 Delegate.Combine 添加订阅，使用 Delegate.Remove 删除订阅。
An event is a pair of methods, for adding and removing subscriptions (actually, it's a trio of methods, but the third method is generally not used for anything). Events themselves do not add anything to the size of an object instance, but the add/remove logic will usually have to add at least one field. The most common default implementation of an event is to create a field of type MultiCastDelegate, and use Delegate.Combine to add subscriptions and Delegate.Remove to remove them.