每15秒执行一次方法，直到它工作为止

Question

我想要一种方法，每15秒检查一次是否连接了特定设备/使用了该设备的驱动程序。

所以类似于：

Every 15 seconds 
{
if (Device is connected)
{
do sth.;
exit loop;
}      
}

到目前为止，我能够创建一个似乎可以工作的计时器：

{
System.Timers.Timer timer = new System.Timers.Timer();
timer.Interval = 15000;
timer.Elapsed += CheckConnection;
timer.Start();
}

不幸的是，一旦我的CheckConnection方法为true/发现设备已连接，我就不知道如何退出/中止计时器。

Answer 1

下面是一个示例应用程序，它展示了如何使用Polly的重试策略来实现所需的行为。

假设您的Device类如下所示：

public class Device
{
private int ConnectionAttempts = 0;
private const int WhenShouldConnectionSucceed = 7;
public bool CheckConnection() => ConnectionAttempts == WhenShouldConnectionSucceed;
public void Connect() => ConnectionAttempts++;
}

• 每次调用Connect方法时，它都会增加ConnectionAttempts
• 当尝试计数器等于预定义值时，CheckConnection将返回true(这模拟成功连接(，否则返回false

重试策略设置如下所示：

var retry = Policy<Device>.HandleResult(result => !result.CheckConnection())
.WaitAndRetryForever(_ => TimeSpan.FromSeconds(15),
onRetry: (result, duration) => Console.WriteLine("Retry has been initiated"));

var device = new Device();
retry.Execute(() =>
{
device.Connect();
return device;
});

• 直到给定的设备未连接(!result.CheckConnection())(，它将永远重试(WaitAndRetryForever(Connect方法
• 在每次重试尝试之间，它等待15秒(TimeSpan.FromSeconds(15)(
• onRetry代表仅用于演示目的。onRetry是可选的

所以，如果我有以下简单的控制台应用程序：

class Program
{
static void Main(string[] args)
{
var retry = Policy<Device>.HandleResult(result => !result.CheckConnection())
.WaitAndRetryForever(_ => TimeSpan.FromSeconds(15),
onRetry: (result, duration) => Console.WriteLine("Retry has been initiated"));
var device = new Device();
retry.Execute(() =>
{
device.Connect();
return device;
});
Console.WriteLine("Device has been connected");
}
}

然后它将在输出中打印以下行：

Retry has been initiated
Retry has been initiated
Retry has been initiated
Retry has been initiated
Retry has been initiated
Retry has been initiated
Device has been connected