扩展与解耦：Option模式与依赖注入结合

参考 ABP设计UI菜单栏的源码分析，抽出了ABP这块自定义扩展的实现。在ABP的源码里面有很多地方都用到了这种设计方式，实现了用户自定义扩展。

新建一个空的asp.net core项目，新建一个类，源码：

using Microsoft.Extensions.Options;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace DesignPatternSample.Infrastructure
{
    public class LanguageInfo
    {
        public string CultureName { get; set; }

        public string DisplayName { get; set; }

        public LanguageInfo(string cultureName, string displayName)
        {
            CultureName = cultureName;
            DisplayName = displayName;
        }

    }

    public class AbpSampleOptions
    {
        public ListLanguages { get; }

        public AbpSampleOptions()
        {
            Languages = new List();
        }
    }

    public interface ILanguageProvider
    {
        Task<IReadOnlyList> GetLanguagesAsync();
    }

    public class DefaultLanguageProvider : ILanguageProvider
    {
        protected AbpSampleOptions Options { get; }

        public DefaultLanguageProvider(IOptionsoptions)
        {
            Options = options.Value;
        }

        public Task<IReadOnlyList> GetLanguagesAsync()
        {
            return Task.FromResult((IReadOnlyList)Options.Languages);
        }
    }
}

StartUp类源码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using DesignPatternSample.Infrastructure;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace DesignPatternSample
{
    public class Startup
    {
        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            // 依赖注入
            services.AddTransient();

            // 配置多语言
            services.Configure(options =>
            {
                options.Languages.Add(new LanguageInfo( "cs", "Čeština"));
                options.Languages.Add(new LanguageInfo("en", "English"));
                options.Languages.Add(new LanguageInfo("pt-BR", "Português"));
                options.Languages.Add(new LanguageInfo("tr", "Türkçe"));
                options.Languages.Add(new LanguageInfo("zh-Hans", "简体中文"));
            });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILanguageProvider provider)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseRouting();
            app.UseEndpoints(endpoints =>
            {
                // 测试
                endpoints.MapGet("/Abp/Test", async context =>
                {
                    var result = provider.GetLanguagesAsync();
                    var output = string.Join(",", result.Result.Select(s => s.CultureName).ToArray());
                    await context.Response.WriteAsync(output);
                });
            });
        }
    }
}

扩展点：在ConfigureService中提供用户自定义扩展点，完美的是下了解耦。