主构造器 primary constructor

C# 12引入

旧的写法

namespace Example.Worker.Service
{
    public class Worker : BackgroundService
    {
        private readonly ILogger<Worker> _logger;

        public Worker(ILogger<Worker> logger)
        {
            _logger = logger;
        }

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            while (!stoppingToken.IsCancellationRequested)
            {
                if (_logger.IsEnabled(LogLevel.Information))
                {
                    _logger.LogInformation("Worker running at: {time}", DateTimeOffset.Now);
                }
                await Task.Delay(1000, stoppingToken);
            }
        }
    }
}

主构造器写法

namespace Example.Worker.Service
{
    // 类直接变成了方法了。
    public class Worker(ILogger<Worker> logger) : BackgroundService
    {
        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            while (!stoppingToken.IsCancellationRequested)
            {
                if (logger.IsEnabled(LogLevel.Information))
                {
                    logger.LogInformation("Worker running at: {time}", DateTimeOffset.Now);
                }
                await Task.Delay(1000, stoppingToken);
            }
        }
    }
}