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      3. 代表如何工作(在后台)?

        How delegates work (in the background)?(代表如何工作(在后台)?)
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                  委托在 C# 中如何在幕后工作以及如何有效地使用它们?

                  How do delegates work in c# behind the scenes and how can they be used efficiently?

                  我知道它们在表面上是如何工作的(它们基本上是函数指针,并允许使用它们的地址调用具有某些签名的回调方法).我需要知道的是 CLR 如何在内部实际实现它们.当您定义委托以及使用委托对象调用回调方法时,幕后究竟发生了什么?

                  I know how they work on the surface(they are basically function pointers and allow callback methods with certain signatures to be invoked using their address). What I need to know is how the CLR actually implements them internally. What exactly happens behind the scenes when you define a delegate and when you invoke a callback method using the delegate object?


                  Re 效率 - 不清楚你的意思,但它们可以通过避免昂贵的反射来实现效率.例如,通过使用 Delegate.CreateDelegate 为动态/查找方法创建(类型化的)预检查委托,而不是使用(较慢的)MethodInfo.Invoke.

                  Re efficiency - it isn't clear what you mean, but they can be used to achieve efficiency, by avoiding expensive reflection. For example, by using Delegate.CreateDelegate to create a (typed) pre-checked delegate to a dynamic/looked-up method, rather than using the (slower) MethodInfo.Invoke.

                  对于一个简单的示例(访问类型的静态 T Parse(string) 模式),请参见下文.请注意,它只使用一次反射(每种类型),而不是很多次.这应该优于反射或典型的 TypeConverter 用法:

                  For a trivial example (accessing the static T Parse(string) pattern for a type), see below. Note that it only uses reflection once (per type), rather than lots of times. This should out-perform either reflection or typical TypeConverter usage:

                  using System;
                  using System.Reflection;
                  static class Program { // formatted for space
                      static void Main() {
                          // do this in a loop to see benefit...
                          int i = Test<int>.Parse("123");
                          float f = Test<float>.Parse("123.45");
                  static class Test<T> {
                      public static T Parse(string text) { return parse(text); }
                      static readonly Func<string, T> parse;
                      static Test() {
                          try {
                              MethodInfo method = typeof(T).GetMethod("Parse",
                                  BindingFlags.Public | BindingFlags.Static,
                                  null, new Type[] { typeof(string) }, null);
                              parse = (Func<string, T>) Delegate.CreateDelegate(
                                  typeof(Func<string, T>), method);
                          } catch (Exception ex) {
                              string msg = ex.Message;
                              parse = delegate { throw new NotSupportedException(msg); };




                  Multicast delegate weird behavior in C#?(C# 中的多播委托奇怪行为?)
                  Parameter count mismatch with Invoke?(参数计数与调用不匹配?)
                  How to store delegates in a List(如何将代表存储在列表中)
                  C# Asynchronous call without EndInvoke?(没有 EndInvoke 的 C# 异步调用?)
                  Delegate.CreateDelegate() and generics: Error binding to target method(Delegate.CreateDelegate() 和泛型:错误绑定到目标方法)
                  Func Delegate vs Function(函数委托与函数)
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