.netcore之DI批量注入(支持泛型)

一旦系统内模块比较多，按DI标准方法去逐个硬敲AddScoped/AddSingleton/AddTransient缺乏灵活性且效率低下，所以批量注入提供了很大的便捷性，特别是对于泛型的服务类，下面介绍一下我在xms系统中应用的DI便捷工具：

1. 先来个dll助手

无外部依赖，可直接复用

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Reflection;
using System.Runtime.Loader;

namespace Xms.Infrastructure.Utility
{
    public class AssemblyHelper
    {
        public static List<Assembly> GetAssemblies(string searchPattern = "")
        {
            List<Assembly> assemblies = new List<Assembly>();
            if (searchPattern.HasValue())
            {
                DirectoryInfo root = new DirectoryInfo(AppDomain.CurrentDomain.BaseDirectory);
                foreach (FileInfo f in root.GetFiles(searchPattern))
                {
                    assemblies.Add(AssemblyLoadContext.Default.LoadFromAssemblyPath(f.FullName));
                }
            }
            else
            {
                assemblies.AddRange(AppDomain.CurrentDomain.GetAssemblies());
            }
            return assemblies;
        }

        public static List<Type> GetClassOfType(Type assignTypeFrom, string searchPattern = "")
        {
            var assemblies = GetAssemblies(searchPattern);
            var result = new List<Type>();
            try
            {
                foreach (var a in assemblies)
                {
                    Type[] types = a.GetTypes();

                    if (types == null)
                    {
                        continue;
                    }

                    foreach (var t in types)
                    {
                        if (!assignTypeFrom.IsAssignableFrom(t) && (!assignTypeFrom.IsGenericTypeDefinition || !DoesTypeImplementOpenGeneric(t, assignTypeFrom)))
                        {
                            continue;
                        }

                        if (t.IsInterface)
                        {
                            continue;
                        }

                        if (t.IsAbstract)
                        {
                            continue;
                        }

                        result.Add(t);
                    }
                }
            }
            catch (ReflectionTypeLoadException ex)
            {
                var msg = string.Empty;
                foreach (var e in ex.LoaderExceptions)
                {
                    msg += e.Message + Environment.NewLine;
                }

                var fail = new Exception(msg, ex);
                Debug.WriteLine(fail.Message, fail);

                throw fail;
            }

            return result;
        }

        public static bool DoesTypeImplementOpenGeneric(Type type, Type openGeneric)
        {
            try
            {
                var genericTypeDefinition = openGeneric.GetGenericTypeDefinition();
                foreach (var implementedInterface in type.FindInterfaces((objType, objCriteria) => true, null))
                {
                    if (!implementedInterface.IsGenericType)
                    {
                        continue;
                    }

                    var isMatch = genericTypeDefinition.IsAssignableFrom(implementedInterface.GetGenericTypeDefinition());
                    return isMatch;
                }

                return false;
            }
            catch
            {
                return false;
            }
        }
    }
}

2. 服务自动注册接口

用于每个模块注册自己的服务，达到模块的高度自治的目的

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

namespace Xms.Infrastructure.Inject
{
    /// <summary>
    /// 服务自动注册接口
    /// </summary>
    public interface IServiceRegistrar
    {
        void Add(IServiceCollection services, IConfiguration configuration);

        int Order { get; }
    }
}

3. DI服务扩展方法

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using System;
using Xms.Infrastructure.Inject;
using Xms.Infrastructure.Utility;

namespace Xms.Core
{
    public static class ServiceCollectionExtensions
    {
        public static IServiceCollection RegisterAll(this IServiceCollection services, IConfiguration configuration)
        {
            var types = AssemblyHelper.GetClassOfType(typeof(IServiceRegistrar), "Xms.*.dll");
            foreach (var t in types)
            {
                var instance = (IServiceRegistrar)Activator.CreateInstance(t);
                instance.Add(services, configuration);
            }
            return services;
        }

        public static IServiceCollection RegisterScope<TService>(this IServiceCollection services)
        {
            var serviceType = typeof(TService);
            return Register(services, serviceType, ServiceLifetime.Scoped);
        }

        public static IServiceCollection RegisterScope(this IServiceCollection services, Type serviceType)
        {
            return Register(services, serviceType, ServiceLifetime.Scoped);
        }

        public static IServiceCollection Register(this IServiceCollection services, Type serviceType, ServiceLifetime serviceLifetime)
        {
            var implementTypes = AssemblyHelper.GetClassOfType(serviceType, "Xms.*.dll");
            if (serviceType.IsGenericType)
            {
                foreach (var impl in implementTypes)
                {
                    var it = impl.FindInterfaces((type, criteria) =>
                    {
                        var isMatch = type.IsGenericType && ((Type)criteria).IsAssignableFrom(type.GetGenericTypeDefinition());
                        return isMatch;
                    }, serviceType);
                    foreach (var i in it)
                    {
                        services.Add(new ServiceDescriptor(i, impl, serviceLifetime));
                    }
                }
            }
            else
            {
                foreach (var impl in implementTypes)
                {
                    services.Add(new ServiceDescriptor(serviceType, impl, serviceLifetime));
                }
            }
            return services;
        }
    }
}

4. 使用示例

比如下面的一个事件发布服务类，多个消费者服务类，实现了消费者的动态注册，大大提高了系统的灵活性、扩展性

    /// <summary>
    /// 事件模块服务注册
    /// </summary>
    public class ServiceRegistrar : IServiceRegistrar
    {
        public int Order => 1;

        public void Add(IServiceCollection services, IConfiguration configuration)
        {
            //event publisher
            services.AddScoped<Event.Abstractions.IEventPublisher, Event.EventPublisher>();
            //event consumers
            services.RegisterScope(typeof(Event.Abstractions.IConsumer<>));
        }
    }