【ABP Source Code Study】Dependency Injection Part

IServiceCollection can replace services.
ServiceDescriptor can generate custom services to be injected using methods like .Scoped().

    public static IServiceCollection AddAbpDynamicOptions<TOptions, TManager>(this IServiceCollection services)
        where TOptions : class
        where TManager : AbpDynamicOptionsManager<TOptions>
    {
        services.Replace(ServiceDescriptor.Scoped(typeof(IOptions<TOptions>), typeof(TManager)));
        services.Replace(ServiceDescriptor.Scoped(typeof(IOptionsSnapshot<TOptions>), typeof(TManager)));

        return services;
    }

Insert the project at the specified position.
To quickly retrieve the services to be used, ABP injects services at the beginning of the container using Insert.

        // Add to the beginning for fast retrieve
        services.Insert(0, ServiceDescriptor.Singleton(typeof(ObjectAccessor<T>), accessor));
        services.Insert(0, ServiceDescriptor.Singleton(typeof(IObjectAccessor<T>), accessor));