1. dotNet1.0
   1. BeginXXX/EndXXX
2. dotNet2.0
   1. Event-Based Asynchronous Programming
   2. Asynchronous Component Pattern
   3. XXXCompleted事件/XXXAsync
3. dotNet4.5
   1. Task-Based Asynchronous Programming:TAP
   2. 基于dotNet4.0中的Task类型
   3. 使用编译器时特性 async和await
   4. 异常处理
   5. 取消

13 Asynchronous Programming