通过使用Timer 方法,您可以在特定时间运行任务,计算当前时间和目标时间之间的时间跨度,并将其作为 DueTime 参数传递。
代码如下:
public Task StartAsync(CancellationToken cancellationToken)
{
//DateTime.Today: 00:00:00
TimeSpan delayTime = DateTime.Today.AddHours(21) - DateTime.Now;
TimeSpan intervalTime = TimeSpan.FromMinutes(1); //86400000s == 1 day
_timer = new Timer(DoWork, null, delayTime, intervalTime);
return Task.CompletedTask;
}
另外,timer或者Task.Delay()方法更适用于在指定的时间间隔执行一个方法,如果你想实现定时任务,我建议你也可以尝试使用Cronos包和Cron Expressions来配置定时任务(参考:链接)。
Cronos 包是一个轻量级但功能齐全的库,用于解析 cron 表达式并在考虑时区和夏令时计算下一次出现。Cronos 是由 HangfireIO 赞助的开源项目,您可以从其 GitHub 存储库中阅读详细文档。详细步骤如下:
通过 NuGet安装Cronos包。
使用以下代码创建 CronJobService 服务:
public abstract class CronJobService : IHostedService, IDisposable
{
private System.Timers.Timer _timer;
private readonly CronExpression _expression;
private readonly TimeZoneInfo _timeZoneInfo;
protected CronJobService(string cronExpression, TimeZoneInfo timeZoneInfo)
{
_expression = CronExpression.Parse(cronExpression);
_timeZoneInfo = timeZoneInfo;
}
public virtual async Task StartAsync(CancellationToken cancellationToken)
{
await ScheduleJob(cancellationToken);
}
protected virtual async Task ScheduleJob(CancellationToken cancellationToken)
{
var next = _expression.GetNextOccurrence(DateTimeOffset.Now, _timeZoneInfo);
if (next.HasValue)
{
var delay = next.Value - DateTimeOffset.Now;
if (delay.TotalMilliseconds <= 0) // prevent non-positive values from being passed into Timer
{
await ScheduleJob(cancellationToken);
}
_timer = new System.Timers.Timer(delay.TotalMilliseconds);
_timer.Elapsed += async (sender, args) =>
{
_timer.Dispose(); // reset and dispose timer
_timer = null;
if (!cancellationToken.IsCancellationRequested)
{
await DoWork(cancellationToken);
}
if (!cancellationToken.IsCancellationRequested)
{
await ScheduleJob(cancellationToken); // reschedule next
}
};
_timer.Start();
}
await Task.CompletedTask;
}
public virtual async Task DoWork(CancellationToken cancellationToken)
{
await Task.Delay(5000, cancellationToken); // do the work
}
public virtual async Task StopAsync(CancellationToken cancellationToken)
{
_timer?.Stop();
await Task.CompletedTask;
}
public virtual void Dispose()
{
_timer?.Dispose();
}
}
public interface IScheduleConfig<T>
{
string CronExpression { get; set; }
TimeZoneInfo TimeZoneInfo { get; set; }
}
public class ScheduleConfig<T> : IScheduleConfig<T>
{
public string CronExpression { get; set; }
public TimeZoneInfo TimeZoneInfo { get; set; }
}
public static class ScheduledServiceExtensions
{
public static IServiceCollection AddCronJob<T>(this IServiceCollection services, Action<IScheduleConfig<T>> options) where T : CronJobService
{
if (options == null)
{
throw new ArgumentNullException(nameof(options), @"Please provide Schedule Configurations.");
}
var config = new ScheduleConfig<T>();
options.Invoke(config);
if (string.IsNullOrWhiteSpace(config.CronExpression))
{
throw new ArgumentNullException(nameof(ScheduleConfig<T>.CronExpression), @"Empty Cron Expression is not allowed.");
}
services.AddSingleton<IScheduleConfig<T>>(config);
services.AddHostedService<T>();
return services;
}
}
创建一个 ScheduleJob.cs:
public class ScheduleJob: CronJobService
{
private readonly ILogger<ScheduleJob> _logger;
public ScheduleJob(IScheduleConfig<ScheduleJob> config, ILogger<ScheduleJob> logger)
: base(config.CronExpression, config.TimeZoneInfo)
{
_logger = logger;
}
public override Task StartAsync(CancellationToken cancellationToken)
{
_logger.LogInformation("ScheduleJob starts.");
return base.StartAsync(cancellationToken);
}
public override Task DoWork(CancellationToken cancellationToken)
{
_logger.LogInformation($"{DateTime.Now:hh:mm:ss} ScheduleJob is working.");
return Task.CompletedTask;
}
public override Task StopAsync(CancellationToken cancellationToken)
{
_logger.LogInformation("ScheduleJob is stopping.");
return base.StopAsync(cancellationToken);
}
}
在 ConfigureServices 方法中注册 ScheduleJob 服务。
public void ConfigureServices(IServiceCollection services)
{
services.AddHostedService<HelloWorldHostedService>();
services.AddCronJob<ScheduleJob>(c=>
{
c.TimeZoneInfo = TimeZoneInfo.Local;
c.CronExpression = @"25 21 * * *"; // 21:25 PM daily.
});
services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
}
然后结果如下: