如何在.Net核心Web作业中读取appsettings.json中的Cron表达式

{
  "CronExpression": "*/5 * * * *"
}

using Microsoft.Extensions.Configuration;

public void ConfigureServices(IServiceCollection services)
{
    // 创建Configuration对象
    var configuration = new ConfigurationBuilder()
        .SetBasePath(Directory.GetCurrentDirectory())
        .AddJsonFile("appsettings.json")
        .Build();

    // 读取Cron表达式配置项
    var cronExpression = configuration.GetValue<string>("CronExpression");

    // 将Cron表达式注册为服务，以便在需要的地方使用
    services.AddSingleton(cronExpression);
}

using Microsoft.Extensions.DependencyInjection;
using NCrontab;

public class MyBackgroundJob
{
    private readonly string _cronExpression;

    public MyBackgroundJob(string cronExpression)
    {
        _cronExpression = cronExpression;
    }

    public void Run()
    {
        var schedule = CrontabSchedule.Parse(_cronExpression);
        var nextRunTime = schedule.GetNextOccurrence(DateTime.Now);

        // 执行定时任务的逻辑
        // ...
    }
}

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        // ...

        // 注册后台作业
        services.AddTransient<MyBackgroundJob>();

        // ...
    }

    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        // ...

        // 获取MyBackgroundJob实例，并执行定时任务
        var job = app.ApplicationServices.GetService<MyBackgroundJob>();
        job.Run();

        // ...
    }
}