通过上面的代码就可以实现基本依赖注入了，但是从功能上来说，上面的代码只支持获取单个服务的实例，不支持注册一个接口的多个实现，获取接口的所有实现，为此对 ServiceContainer 中的 Instance 的 ConcurrentDictionary 的 Key 进行一下改造，使得可以能够以接口类型和实现类型联合作为 key，为此就有了第二版的 ServiceContainer
ServiceContainer v2为此定义了一个 ServiceKey 的类型，请注意这里一定要重写 GetHashCode 方法：
private class ServiceKey : IEquatable<ServiceKey> { public Type ServiceType { get; } public Type ImplementType { get; } public ServiceKey(Type serviceType, ServiceDefinition definition) { ServiceType = serviceType; ImplementType = definition.GetImplementType(); } public bool Equals(ServiceKey other) { return ServiceType == other?.ServiceType && ImplementType == other?.ImplementType; } public override bool Equals(object obj) { return Equals((ServiceKey)obj); } public override int GetHashCode() { var key = $"{ServiceType.FullName}_{ImplementType.FullName}"; return key.GetHashCode(); } }第二版的 ServiceContainer :
public class ServiceContainer : IServiceContainer { internal readonly ConcurrentBag<ServiceDefinition> _services; private readonly ConcurrentDictionary<ServiceKey, object> _singletonInstances; private readonly ConcurrentDictionary<ServiceKey, object> _scopedInstances; private ConcurrentBag<object> _transientDisposables = new ConcurrentBag<object>(); private class ServiceKey : IEquatable<ServiceKey> { public Type ServiceType { get; } public Type ImplementType { get; } public ServiceKey(Type serviceType, ServiceDefinition definition) { ServiceType = serviceType; ImplementType = definition.GetImplementType(); } public bool Equals(ServiceKey other) { return ServiceType == other?.ServiceType && ImplementType == other?.ImplementType; } public override bool Equals(object obj) { return Equals((ServiceKey)obj); } public override int GetHashCode() { var key = $"{ServiceType.FullName}_{ImplementType.FullName}"; return key.GetHashCode(); } } private readonly bool _isRootScope; public ServiceContainer() { _isRootScope = true; _singletonInstances = new ConcurrentDictionary<ServiceKey, object>(); _services = new ConcurrentBag<ServiceDefinition>(); } private ServiceContainer(ServiceContainer serviceContainer) { _isRootScope = false; _singletonInstances = serviceContainer._singletonInstances; _services = serviceContainer._services; _scopedInstances = new ConcurrentDictionary<ServiceKey, object>(); } public IServiceContainer Add(ServiceDefinition item) { if (_disposed) { throw new InvalidOperationException("the service container had been disposed"); } if (_services.Any(_ => _.ServiceType == item.ServiceType && _.GetImplementType() == item.GetImplementType())) { return this; } _services.Add(item); return this; } public IServiceContainer TryAdd(ServiceDefinition item) { if (_disposed) { throw new InvalidOperationException("the service container had been disposed"); } if (_services.Any(_ => _.ServiceType == item.ServiceType)) { return this; } _services.Add(item); return this; } public IServiceContainer CreateScope() { return new ServiceContainer(this); } private bool _disposed; public void Dispose() { if (_disposed) { return; } if (_isRootScope) { lock (_singletonInstances) { if (_disposed) { return; } _disposed = true; foreach (var instance in _singletonInstances.Values) { (instance as IDisposable)?.Dispose(); } foreach (var o in _transientDisposables) { (o as IDisposable)?.Dispose(); } _singletonInstances.Clear(); _transientDisposables = null; } } else { lock (_scopedInstances) { if (_disposed) { return; } _disposed = true; foreach (var instance in _scopedInstances.Values) { (instance as IDisposable)?.Dispose(); } foreach (var o in _transientDisposables) { (o as IDisposable)?.Dispose(); } _scopedInstances.Clear(); _transientDisposables = null; } } } private object GetServiceInstance(Type serviceType, ServiceDefinition serviceDefinition) { if (serviceDefinition.ImplementationInstance != null) return serviceDefinition.ImplementationInstance; if (serviceDefinition.ImplementationFactory != null) return serviceDefinition.ImplementationFactory.Invoke(this); var implementType = (serviceDefinition.ImplementType ?? serviceType); if (implementType.IsInterface || implementType.IsAbstract) { throw new InvalidOperationException($"invalid service registered, serviceType: {serviceType.FullName}, implementType: {serviceDefinition.ImplementType}"); } if (implementType.IsGenericType) { implementType = implementType.MakeGenericType(serviceType.GetGenericArguments()); } var ctorInfos = implementType.GetConstructors(BindingFlags.Instance | BindingFlags.Public); if (ctorInfos.Length == 0) { throw new InvalidOperationException($"service {serviceType.FullName} does not have any public constructors"); } ConstructorInfo ctor; if (ctorInfos.Length == 1) { ctor = ctorInfos[0]; } else { // TODO: try find best ctor ctor = ctorInfos .OrderBy(_ => _.GetParameters().Length) .First(); } var parameters = ctor.GetParameters(); if (parameters.Length == 0) { // TODO: cache New Func return Expression.Lambda<Func<object>>(Expression.New(ctor)).Compile().Invoke(); } else { var ctorParams = new object[parameters.Length]; for (var index = 0; index < parameters.Length; index++) { var parameter = parameters[index]; var param = GetService(parameter.ParameterType); if (param == null && parameter.HasDefaultValue) { param = parameter.DefaultValue; } ctorParams[index] = param; } return Expression.Lambda<Func<object>>(Expression.New(ctor, ctorParams.Select(Expression.Constant))).Compile().Invoke(); } } public object GetService(Type serviceType) { if (_disposed) { throw new InvalidOperationException($"can not get scope service from a disposed scope, serviceType: {serviceType.FullName}"); } var serviceDefinition = _services.LastOrDefault(_ => _.ServiceType == serviceType); if (null == serviceDefinition) { if (serviceType.IsGenericType) { var genericType = serviceType.GetGenericTypeDefinition(); serviceDefinition = _services.LastOrDefault(_ => _.ServiceType == genericType); if (null == serviceDefinition) { var innerServiceType = serviceType.GetGenericArguments().First(); if (typeof(IEnumerable<>).MakeGenericType(innerServiceType) .IsAssignableFrom(serviceType)) { var innerRegType = innerServiceType; if (innerServiceType.IsGenericType) { innerRegType = innerServiceType.GetGenericTypeDefinition(); } // var list = new List<object>(4); foreach (var def in _services.Where(_ => _.ServiceType == innerRegType)) { object svc; if (def.ServiceLifetime == ServiceLifetime.Singleton) { svc = _singletonInstances.GetOrAdd(new ServiceKey(innerServiceType, def), (t) => GetServiceInstance(innerServiceType, def)); } else if (def.ServiceLifetime == ServiceLifetime.Scoped) { svc = _scopedInstances.GetOrAdd(new ServiceKey(innerServiceType, def), (t) => GetServiceInstance(innerServiceType, def)); } else { svc = GetServiceInstance(innerServiceType, def); if (svc is IDisposable) { _transientDisposables.Add(svc); } } if (null != svc) { list.Add(svc); } } var methodInfo = typeof(Enumerable) .GetMethod("Cast", BindingFlags.Static | BindingFlags.Public); if (methodInfo != null) { var genericMethod = methodInfo.MakeGenericMethod(innerServiceType); var castedValue = genericMethod.Invoke(null, new object[] { list }); if (typeof(IEnumerable<>).MakeGenericType(innerServiceType) == serviceType) { return castedValue; } var toArrayMethod = typeof(Enumerable).GetMethod("ToArray", BindingFlags.Static | BindingFlags.Public) .MakeGenericMethod(innerServiceType); return toArrayMethod.Invoke(null, new object[] { castedValue }); } return list; } return null; } } else { return null; } } if (_isRootScope && serviceDefinition.ServiceLifetime == ServiceLifetime.Scoped) { throw new InvalidOperationException($"can not get scope service from the root scope, serviceType: {serviceType.FullName}"); } if (serviceDefinition.ServiceLifetime == ServiceLifetime.Singleton) { var svc = _singletonInstances.GetOrAdd(new ServiceKey(serviceType, serviceDefinition), (t) => GetServiceInstance(t.ServiceType, serviceDefinition)); return svc; } else if (serviceDefinition.ServiceLifetime == ServiceLifetime.Scoped) { var svc = _scopedInstances.GetOrAdd(new ServiceKey(serviceType, serviceDefinition), (t) => GetServiceInstance(t.ServiceType, serviceDefinition)); return svc; } else { var svc = GetServiceInstance(serviceType, serviceDefinition); if (svc is IDisposable) { _transientDisposables.Add(svc); } return svc; } } }这样我们就不仅支持了 IEnumerable<TService> 的注册，也支持 IReadOnlyList<TService>/ IReadOnlyCollection<TService> 的注册