在应用程序启动期间，我使用CarService类来检索数据。我只想这样做一次，结果List<Car>从那一点起对应用中的所有消费者都可用（使用DI），换句话说，我不想每次在控制器或服务中注入ICarService时调用CarService -> GetData，而是只调用一次。

public interface ICarService
{
   Task<List<Car>> GetData();
}

public class CarService : ICarService
{
   private readonly IHttpClientFactory _httpClientFactory;

   public CarService(IHttpClientFactory httpClientFactory)
   {
      _httpClientFactory = httpClientFactory;
   }

   public async Task<List<Car>> GetData()
   { 
      var client = _httpClientFactory.CreateClient();
      var req = new HttpRequestMessage(HttpMethod.Get, "https://localhost:5011/cars");        
      var res = await client.SendAsync(req);
      ...
      return data;
   }
}

Program.cs

services.AddSingleton<ICarService, CarService>();
services.AddHostedService<GetDataService>();

public class GetDataService : IHostedService
{
    public async Task StartAsync(CancellationToken cancellationToken)
    {
        var carService = _serviceScopeFactory.CreateScope().ServiceProvider
            .GetRequiredService<ICarService>();
        var data = carService.GetData();
        ...
    }    
}