lock 锁的使用场景

  public class ProductService : IProductService
  {
      private readonly object _locker = new object();
      private readonly IMemoryCache _memoryCache;
      public ProductService(IMemoryCache memoryCache)
      {
          _memoryCache = memoryCache;
      }
      public IEnumerable<Product> GetProducts()
      {
          List<Product> products;
          if (!_memoryCache.TryGetValue("Products", out products))
          {
              if (!_memoryCache.TryGetValue("Products", out products))
              {//当内存中不存在是，则从数据库中获取数据
                  lock (_locker)
                  {//当创建缓存时，需要加锁，防止多个线程同时创建缓存
                      products = new List<Product>
                      {
                          new Product { Id = 1, Name = "Product 1" },
                          new Product { Id = 2, Name = "Product 2" },
                          new Product { Id = 3, Name = "Product 3" }
                      };
                      _memoryCache.Set("Products", products, new MemoryCacheEntryOptions
                      {
                          AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(10)
                      });
                  }
              }
          }
          return products;
      }
  }

  public interface IProductService
  {
      IEnumerable<Product> GetProducts();
  }

  public class Product
  {
      public int Id { get; set; }
      public string Name { get; set; }
  }