擴展與解耦：Option模式與依賴註入結合

參考 ABP設計UI菜單欄的源碼分析，抽出了ABP這塊自定義擴展的實現。在ABP的源碼裡面有很多地方都用到了這種設計方式，實現了用戶自定義擴展。

新建一個空的asp.net core項目，新建一個類，源碼：

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 List<LanguageInfo> Languages { get; }

        public AbpSampleOptions()
        {
            Languages = new List<LanguageInfo>();
        }
    }

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

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

        public DefaultLanguageProvider(IOptions<AbpSampleOptions> options)
        {
            Options = options.Value;
        }

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

StartUp類源碼：

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)
        {
            // 依賴註入
            services.AddTransient<ILanguageProvider, DefaultLanguageProvider>();

            // 配置多語言
            services.Configure<AbpSampleOptions>(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", "簡體中文"));
            });
        }

        // 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 =>
            {
                // 測試
                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);
                });
            });
        }
    }
}

擴展點：在ConfigureService中提供用戶自定義擴展點，完美的是下瞭解耦。

參考：

BookStore示例項目---菜單欄UI分析

Options模式的應用