我需要知道＃如果在C＃中使用...谢谢..

I need to know the usage of #if in C#...Thanks..

推荐答案

＃如果是 pre-处理器命令。

这是最常见的用法（其中有人可能会说是滥用）是有code，只有编译在调试模式下：

It's most common usage (which some might say is an abuse) is to have code that only compiles in debug mode:

#if DEBUG
    Console.WriteLine("Here");
#endif

一个很好的使用（如StingJack指出的）是允许Windows服务的调试简单：

One very good use (as StingJack points out) is to allow easy debugging of a Windows Service:

static void Main()
{
#if (!DEBUG)
    System.ServiceProcess.ServiceBase[] ServicesToRun;
    ServicesToRun = new System.ServiceProcess.ServiceBase[] { new Service1() };
    System.ServiceProcess.ServiceBase.Run(ServicesToRun);
#else
    // Debug code: this allows the process to run as a non-service.

    // It will kick off the service start point, but never kill it.

    // Shut down the debugger to exit

    Service1 service = new Service1();
    service.<Your Service's Primary Method Here>();
    // Put a breakpoint on the following line to always catch
    // your service when it has finished its work
    System.Threading.Thread.Sleep(System.Threading.Timeout.Infinite);
#endif 
}

来源

这意味着运行释放模式将启动该服务符合预期，而在调试模式下运行将让你真正调试code。

This means that running release mode will start the service as expected, while running in debug mode will allow you to actually debug the code.