An unhandled exception occurred while processing the request.
InvalidOperationException: Unable to resolve service for type 'System.Lazy`1[WebApplication9.Services.IValuesService]' while attempting to activate 'WebApplication9.Controllers.ValuesController'.
Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetService(IServiceProvider sp, Type type, Type requiredBy, bool isDefaultParameterRequired)
class Program
static void Main(string[] args)
var services = new ServiceCollection();
services.AddScoped<ITestService, TestService>();
services.AddTransient(typeof(Lazy<>));
var serviceProvider = services.BuildServiceProvider();
using (var scope = serviceProvider.CreateScope() )
var service = scope.ServiceProvider.GetService<Lazy<ITestService>>();
// 这边令人遗憾地输出了true，也就是说，这种方式的延迟注入是失败的
Console.WriteLine(service.IsValueCreated);
public class LazyLoader<T> : Lazy<T>
public LazyLoader(IServiceProvider sp) : base(sp.GetRequiredService<T>)
class Program
static void Main(string[] args)
var services = new ServiceCollection();
services.AddScoped<ITestService, TestService>();
// services.AddScoped(typeof(Lazy<>), typeof(LazyLoader<>)); 也可以，区别不大
services.AddTransient(typeof(Lazy<>), typeof(LazyLoader<>));
var serviceProvider = services.BuildServiceProvider();
using (var scope = serviceProvider.CreateScope())
var service = scope.ServiceProvider.GetService<Lazy<ITestService>>();
Console.WriteLine(service.IsValueCreated); // 输出false
// 下面输出true，延迟注入的对象和正常注入的对象，本质上不会有差别
Console.WriteLine(service.Value == scope.ServiceProvider.GetService<ITestService>());
