.net core 依赖注入 DependencyInjection

.net core 依赖注入源码位于.net core的runtime源码 中 ，其他源码信息 

.net core独立模块源码：https://github.com/aspnet

.net core全家桶源码：https://github.com/dotnet/aspnetcore

.net core拓展库源码：https://github.com/dotnet/extensions

.net core标准库源码：https://github.com/dotnet/corefx

.net core的EFCore源码：https://github.com/dotnet/efcore

.net core的SDK源码：https://github.com/dotnet/sdk

.net core的runtime源码：https://github.com/dotnet/runtime

依赖注入模块主要的2个类 IServiceCollection 和  IServiceProvider

1.IServiceCollection源码

 /// <summary>
 /// Specifies the contract for a collection of service descriptors.
 /// </summary>
 public interface IServiceCollection : IList<ServiceDescriptor>
 {
 }

  [DebuggerDisplay("{DebuggerToString(),nq}")]
  [DebuggerTypeProxy(typeof(ServiceCollectionDebugView))]
  public class ServiceCollection : IServiceCollection
  {
      private readonly List<ServiceDescriptor> _descriptors = new List<ServiceDescriptor>();
      private bool _isReadOnly;

     .....
  }

ServiceCollection中包含一组 ServiceDescriptor，用于记录注册类的描述信息，

 public class ServiceDescriptor

{


   private ServiceDescriptor(Type serviceType, object? serviceKey, ServiceLifetime lifetime)
   {
       Lifetime = lifetime;
       ServiceType = serviceType;
       ServiceKey = serviceKey;
   }

   /// <summary>
   /// Gets the <see cref="ServiceLifetime"/> of the service.
   /// </summary>
   public ServiceLifetime Lifetime { get; }

   /// <summary>
   /// Get the key of the service, if applicable.
   /// </summary>
   public object? ServiceKey { get; }

   /// <summary>
   /// Gets the <see cref="Type"/> of the service.
   /// </summary>
   public Type ServiceType { get; }

   [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)]
   private Type? _implementationType;

   /// <summary>
   /// Gets the <see cref="Type"/> that implements the service.
   /// </summary>
   [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)]
   public Type? ImplementationType
   {
       get
       {
           if (IsKeyedService)
           {
               ThrowKeyedDescriptor();
           }
           return _implementationType;
       }
   }

   /// <summary>
   /// Gets the <see cref="Type"/> that implements the service.
   /// </summary>
   [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)]
   public Type? KeyedImplementationType
   {
       get
       {
           if (!IsKeyedService)
           {
               ThrowNonKeyedDescriptor();
           }
           return _implementationType;
       }
   }

   private object? _implementationInstance;

   /// <summary>
   /// Gets the instance that implements the service.
   /// </summary>
   public object? ImplementationInstance
   {
       get
       {
           if (IsKeyedService)
           {
               ThrowKeyedDescriptor();
           }
           return _implementationInstance;
       }
   }

   /// <summary>
   /// Gets the instance that implements the service.
   /// </summary>
   public object? KeyedImplementationInstance
   {
       get
       {
           if (!IsKeyedService)
           {
               ThrowNonKeyedDescriptor();
           }
           return _implementationInstance;
       }
   }

   private object? _implementationFactory;

   /// <summary>
   /// Gets the factory used for creating service instances.
   /// </summary>
   public Func<IServiceProvider, object>? ImplementationFactory
   {
       get
       {
           if (IsKeyedService)
           {
               ThrowKeyedDescriptor();
           }
           return (Func<IServiceProvider, object>?) _implementationFactory;
       }
   }

   /// <summary>
   /// Gets the factory used for creating Keyed service instances.
   /// </summary>
   public Func<IServiceProvider, object?, object>? KeyedImplementationFactory
   {
       get
       {
           if (!IsKeyedService)
           {
               ThrowNonKeyedDescriptor();
           }
           return (Func<IServiceProvider, object?, object>?) _implementationFactory;
       }
   }

   /// <summary>
   /// Indicates whether the service is a keyed service.
   /// </summary>
   public bool IsKeyedService => ServiceKey != null;

}