C# Invoke 和 DynamicInvoke 之间的区别
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Difference Between Invoke and DynamicInvoke
提问by testCoder
What is the difference between Invoke and DynamicInvoke in delegates? Please give me some code example which explain difference between that two methods.
委托中的 Invoke 和 DynamicInvoke 有什么区别？请给我一些代码示例来解释这两种方法之间的区别。
采纳答案by Marc Gravell
When you have a delegate instance, you might know the exact type, or you might just know that it is a Delegate. If you know the exact type, you can use Invoke, which is very fast- everything is already pre-validated. For example:
当您有一个委托实例时，您可能知道确切的类型，或者您可能只知道它是一个Delegate. 如果您知道确切的类型，则可以使用Invoke，这非常快- 一切都已经过预先验证。例如：
Func<int,int> twice = x => x * 2;
int i = 3;
int j = twice.Invoke(i);
// or just:
int j = twice(i);
However! If you just know that it is Delegate, it has to resolve the parameters etc manually - this might involve unboxing, etc - a lot of reflection is going on. For example:
然而！如果您只知道它是Delegate，它必须手动解析参数等 - 这可能涉及拆箱等 - 正在进行大量反射。例如：
Delegate slowTwice = twice; // this is still the same delegate instance
object[] args = { i };
object result = slowTwice.DynamicInvoke(args);
Note I've written the argslong hand to make it clear that an object[]is involved. There are lots of extra costs here:
请注意，我写了args长篇大论以明确表示object[]涉及an 。这里有很多额外的费用：
- the array
- validating the passed arguments are a "fit" for the actual
MethodInfo - unboxing etc as necessary
- reflection-invoke
- then the caller needs to do something to process the return value
- 数组
- 验证传递的参数是否“适合”实际
MethodInfo - 必要时拆箱等
- 反射调用
- 那么调用者需要做一些事情来处理返回值
Basically, avoid DynamicInvokewhen-ever you can. Invokeis always preferable, unless all you have is a Delegateand an object[].
基本上，尽可能避免DynamicInvoke。Invoke总是可取的，除非你只有一个Delegate和一个object[]。
For a performance comparison, the following in release mode outside of the debugger (a console exe) prints:
为了进行性能比较，在调试器（控制台 exe）之外的发布模式下打印以下内容：
Invoke: 19ms
DynamicInvoke: 3813ms
Code:
代码：
Func<int,int> twice = x => x * 2;
const int LOOP = 5000000; // 5M
var watch = Stopwatch.StartNew();
for (int i = 0; i < LOOP; i++)
{
twice.Invoke(3);
}
watch.Stop();
Console.WriteLine("Invoke: {0}ms", watch.ElapsedMilliseconds);
watch = Stopwatch.StartNew();
for (int i = 0; i < LOOP; i++)
{
twice.DynamicInvoke(3);
}
watch.Stop();
Console.WriteLine("DynamicInvoke: {0}ms", watch.ElapsedMilliseconds);
