NextStep = 1;

while(ManualEventSet.WaitOne())
{
Process();
Thread.Sleep(20);
}

void Process()
{
switch(nextStep)
{
case 1:
DoSomething;
break; // 会一直执行这个Step

		    // 正常流程的下一步
		    nextStep = 2;
			
			// 失败了可以跳到统一的错误处理
		 break;
		 case 2:
		   nextStep = 3;
		 break;
		 case 3:
		    
		 break;
		 case 4:
		 break;
  }

}