services.AddDbContext<xxxDbContext>(dbContextOptionsBuilder =>dbContextOptionsBuilder.UseSqlServer(Configuration.GetConnectionString("The name of the connection string in the configuration file.")));
// Or
services.AddDbContext<xxxDbContext>((serviceProvider, dbContextOptionsBuilder) =>
{var service = serviceProvider.GetService<xxx>();dbContextOptionsBuilder.UseSqlServer(Configuration.GetConnectionString("The name of the connection string in the configuration file.");
});

如果我们仔细研究AddDbContext 扩展方法的参数，我们会发现它是一个action，通过Action，我们可以封装一个方法、委托、内联委托、lambda等。

public class Program
{public static void Main(string[] args){CreateHostBuilder(args).Build().Run();}public static IHostBuilder CreateHostBuilder(string[] args) => Host.CreateDefaultBuilder(args).ConfigureAppConfiguration((hostingContext, config) => { }).ConfigureWebHostDefaults(webBuilder =>{webBuilder.ConfigureServices(services =>{services.AddControllersWithViews();// ...}).Configure(app =>{if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}else{// ...}// ...});});
}

2.使用Startup配置服务

public class Startup
{public Startup(IConfiguration configuration){Configuration = configuration;}public IConfiguration Configuration { get; }public void ConfigureServices(IServiceCollection services){services.AddRazorPages();// ...}public void Configure(IApplicationBuilder app, IWebHostEnvironment env){if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}else{app.UseExceptionHandler("/Error");app.UseHsts();}//...}
}

当我们启动ASP.NET Core应用程序时，ASP.NET Core将创建Startup类的新实例，并调用ConfigureServices 方法来创建其服务。然后，它调用Configure 方法，该方法设置请求管道以处理传入的HTTP请求。

public class Program
{public static void Main(string[] args){BuildWebHost(args).Run();}public static IWebHost BuildWebHost(string[] args){WebHost.CreateDefaultBuilder(args).UseStartup<Startup>().Build();}
}

因此，我们程序中的Startup类最初将如下所示：

public class Startup
{public Startup(IConfiguration configuration){Configuration = configuration;}public IConfiguration Configuration { get; }public void ConfigureServices(IServiceCollection services){// ...services.AddDbContext<xxxDbContext>(dbContextOptionsBuilder =>dbContextOptionsBuilder.UseSqlServer(Configuration.GetConnectionString("The name of the connection string in the configuration file.")));//Orservices.AddDbContext<xxxDbContext>((serviceProvider, dbContextOptionsBuilder) =>{var service = serviceProvider.GetService<xxx>();dbContextOptionsBuilder.UseSqlServer(Configuration.GetConnectionString("The name of the connection string in the configuration file."));});// ...}public void Configure(IApplicationBuilder app, IWebHostEnvironment env){if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}//...}
}

但是，这样的DbContext 会在小型程序中找到，有时在中等程序中也会出现，但是在大型程序中，将很难用一个DbContext来管理该程序。

public class Startup
{// ...public void ConfigureServices(IServiceCollection services){// ...services.AddDbContextPool<DbContextA>(dbContextOptionsBuilder =>dbContextOptionsBuilder.UseSqlServer(Configuration.GetConnectionString("The name of the connection string in the configuration file."))).AddDbContextPool<DbContextB>(dbContextOptionsBuilder =>dbContextOptionsBuilder.UseSqlServer(Configuration.GetConnectionString("The name of the connection string in the configuration file."))).AddDbContextPool<DbContextC>(dbContextOptionsBuilder =>dbContextOptionsBuilder.UseSqlServer(Configuration.GetConnectionString("The name of the connection string in the configuration file.")));// ...}// ...
}

DbContextConfigurer模式

public class ConnectionStringsOptions : IOptions<ConnectionStringsOptions>
{public const string KEY_NAME = "ConnectionStringsOptions";public ConnectionStringsOptions() : this(null, null, null, null) { }public ConnectionStringsOptions(string serverName, string databaseName,string userId, string password){ServerName = serverName;DatabaseName = databaseName;UserId = userId;Password = password;}public string ServerName { get; set; }public string DatabaseName { get; set; }public string UserId { get; set; }public string Password { get; set; }ConnectionStringsOptions IOptions<ConnectionStringsOptions>.Value => this;
}public static class EntityFrameworkProviders
{public static string SqlServer = "SQL-SERVER";public static string SQLite = "SQLITE";public static string InMemor = "IN-MEMOR";
}public class EntityFrameworkOptions : IOptions<EntityFrameworkOptions>
{public const string KEY_NAME = "EntityFrameworkOptions";public EntityFrameworkOptions() : this(EntityFrameworkProviders.SqlServer, true) { }public EntityFrameworkOptions(string provider, bool canMigrate){Provider = provider;CanMigrate = canMigrate;}public string Provider { get; set; }/// <summary>/// In some providers, we must not execute migration/// </summary>public bool CanMigrate { get; set; }EntityFrameworkOptions IOptions<EntityFrameworkOptions>.Value => this;
}

要使用当前结构，我们必须对appsettings.json和appsettings.Development.json进行一些更改。如下所示：

// appsettings.json
{"EntityFrameworkOptions": {"Provider": "SQL-SERVER","CanMigrate": true},"ConnectionStringsOptions": {"ServerName": "xxx.database.windows.net","DatabaseName": "xxx","UserId": "xxx_Developers","Password": "xxxx-xxx-xxx-xxx"}
}
//appsettings.Development.json
{"EntityFrameworkOptions": {"Provider": "SQLITE","CanMigrate": true},"ConnectionStringsOptions": {"ServerName": null,"DatabaseName": "dev.db","UserId": null,"Password": null}
}

当我们需要访问强类型设置时，我们只需要将IOptions <>类的实例注入到我们消费类的构造函数中，然后让依赖项注入处理其余部分：

using System.Collections.Generic;
using ConfigureEFDbContext.Options;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Options;namespace ConfigureEFDbContext.Controllers
{[ApiController][Route("[controller]")]public class OptionsPatternController : ControllerBase{private readonly EntityFrameworkOptions _entityFrameworkOptions;private readonly ConnectionStringsOptions _connectionStringsOptions;public OptionsPatternController(IOptions<EntityFrameworkOptions>entityFrameworkOptions, IOptions<ConnectionStringsOptions> connectionStringsOptions){_entityFrameworkOptions = entityFrameworkOptions.Value;_connectionStringsOptions = connectionStringsOptions.Value;}[HttpGet]public IEnumerable<string> Get() => new[] { _entityFrameworkOptions.Provider,_connectionStringsOptions.DatabaseName };}
}

DbContext配置工厂模式

using System;
using System.Collections.Generic;
using System.Reflection;
using ConfigureEFDbContext.EFProviderConnectionOptions;
using ConfigureEFDbContext.Options;
using Microsoft.Extensions.Options;namespace ConfigureEFDbContext
{public interface IDbContextConfigurerFactory{IDbContextConfigurer GetConfigurer(string migrationsAssembly = null);}public class DbContextConfigurerFactory : IDbContextConfigurerFactory{public DbContextConfigurerFactory(IOptions<EntityFrameworkOptions> options,IEntityFrameworkProviderConnectionOptions dbProviderConnectionOptions){EntityFrameworkOptions = options.Value;Factories = new Dictionary<string, Func<string, IDbContextConfigurer>>() {{EntityFrameworkProviders.SqlServer, (migrationsAssembly) =>CreateSqlServerSetup(dbProviderConnectionOptions, migrationsAssembly)},{EntityFrameworkProviders.SQLite, (migrationsAssembly) =>CreateSqliteSetup(dbProviderConnectionOptions, migrationsAssembly)},{EntityFrameworkProviders.InMemor, (migrationsAssembly) =>CreateInMemorySetup(dbProviderConnectionOptions, migrationsAssembly)},};}protected EntityFrameworkOptions EntityFrameworkOptions { get; }protected Dictionary<string, Func<string, IDbContextConfigurer>> Factories { get; }public virtual IDbContextConfigurer GetConfigurer(string migrationsAssembly = null)=> Factories.ContainsKey(EntityFrameworkOptions.Provider)? Factories[EntityFrameworkOptions.Provider](migrationsAssembly ?? Assembly.GetCallingAssembly().GetName().Name): default;protected virtual IDbContextConfigurer CreateSqlServerConfigurer(IEntityFrameworkProviderConnectionOptions dbProviderConnectionOptions,string migrationsAssembly) => new SqlServerDbContextConfigurer(dbProviderConnectionOptions, migrationsAssembly);protected virtual IDbContextConfigurer CreateSqliteConfigurer(IEntityFrameworkProviderConnectionOptions dbProviderConnectionOptions,string migrationsAssembly) => new SqliteDbContextConfigurer(dbProviderConnectionOptions, migrationsAssembly);protected virtual IDbContextConfigurer CreateInMemoryConfigurer(IEntityFrameworkProviderConnectionOptions dbProviderConnectionOptions,string migrationsAssembly) => new InMemoryDbContextConfigurer(dbProviderConnectionOptions, migrationsAssembly);}public class CacheableDbContextConfigurerFactory : DbContextConfigurerFactory{protected IDbContextConfigurer _sqlServerConfigurer;protected IDbContextConfigurer _sqliteConfigurer;protected IDbContextConfigurer _inMemoryConfigurer;public CacheableDbContextConfigurerFactory(IOptions<EntityFrameworkOptions> options,IEntityFrameworkProviderConnectionOptions dbProviderConnectionOptions) :base(options, dbProviderConnectionOptions) { }protected override IDbContextConfigurer CreateSqlServerConfigurer(IEntityFrameworkProviderConnectionOptions dbProviderConnectionOptions,string migrationsAssembly) => _sqlServerConfigurer ??= base.CreateSqlServerSetup(dbProviderConnectionOptions, migrationsAssembly);protected override IDbContextConfigurer CreateSqliteConfigurer(IEntityFrameworkProviderConnectionOptions dbProviderConnectionOptions,string migrationsAssembly) => _sqliteConfigurer ??= base.CreateSqliteSetup(dbProviderConnectionOptions, migrationsAssembly);protected override IDbContextConfigurer CreateInMemoryConfigurer(IEntityFrameworkProviderConnectionOptions dbProviderConnectionOptions,string migrationsAssembly) => _inMemoryConfigurer ??= base.CreateInMemorySetup(dbProviderConnectionOptions, migrationsAssembly);}
}

这是Product接口和具体类的实现：

using System;
using ConfigureEFDbContext.EFProviderConnectionOptions;
using Microsoft.EntityFrameworkCore;namespace ConfigureEFDbContext
{public interface IDbContextConfigurer{void Configure(IServiceProvider serviceProvider, DbContextOptionsBuilder builder);}public abstract class DbContextConfigurer : IDbContextConfigurer{protected DbContextConfigurer(IEntityFrameworkProviderConnectionOptions dbProviderConnectionOptions,string migrationsAssembly){DbProviderConnectionOptions = dbProviderConnectionOptions;MigrationsAssembly = migrationsAssembly;}public IEntityFrameworkProviderConnectionOptions DbProviderConnectionOptions { get; }public string MigrationsAssembly { get; }public abstract void Configure(IServiceProvider serviceProvider,DbContextOptionsBuilder builder);}public class SqlServerDbContextConfigurer : DbContextConfigurer{public SqlServerDbContextConfigurer(IEntityFrameworkProviderConnectionOptions dbProviderConnectionOptions,string migrationsAssembly) : base(dbProviderConnectionOptions, migrationsAssembly) { }public override void Configure(IServiceProvider serviceProvider,DbContextOptionsBuilder builder){if (DbProviderConnectionOptions.UseConnectionString){builder.UseSqlServer(connectionString: DbProviderConnectionOptions.GetConnectionString(),sqlServerDbContextOptionsBuilder =>sqlServerDbContextOptionsBuilder.MigrationsAssembly(MigrationsAssembly));}else{builder.UseSqlServer(connection: DbProviderConnectionOptions.GetConnection(),sqlServerDbContextOptionsBuilder =>sqlServerDbContextOptionsBuilder.MigrationsAssembly(MigrationsAssembly));}}}public class SqliteDbContextConfigurer : DbContextConfigurer{public SqliteDbContextConfigurer(IEntityFrameworkProviderConnectionOptions dbProviderConnectionOptions,string migrationsAssembly) : base(dbProviderConnectionOptions, migrationsAssembly) { }public override void Configure(IServiceProvider serviceProvider,DbContextOptionsBuilder builder){if (DbProviderConnectionOptions.UseConnectionString){builder.UseSqlite(connectionString: DbProviderConnectionOptions.GetConnectionString(),sqlServerDbContextOptionsBuilder =>sqlServerDbContextOptionsBuilder.MigrationsAssembly(MigrationsAssembly));}else{builder.UseSqlite(connection: DbProviderConnectionOptions.GetConnection(),sqlServerDbContextOptionsBuilder =>sqlServerDbContextOptionsBuilder.MigrationsAssembly(MigrationsAssembly));}}}public class InMemoryDbContextConfigurer : DbContextConfigurer{public InMemoryDbContextConfigurer(IEntityFrameworkProviderConnectionOptionsdbProviderConnectionOptions, string migrationsAssembly) :base(dbProviderConnectionOptions, migrationsAssembly) { }public override void Configure(IServiceProvider serviceProvider,DbContextOptionsBuilder builder) => builder.UseInMemoryDatabase(DbProviderConnectionOptions.GetConnectionString());}
}

这个工厂负责通过调用GetConfigurer方法创建将配置DbContext的类，我们将获得一个包含该Configure 方法的IDbContextConfigurer实例来初始化DbContext。

using System.Data.Common;
using ConfigureEFDbContext.Common;
using ConfigureEFDbContext.Options;
using Microsoft.Data.Sqlite;
using Microsoft.Extensions.Options;namespace ConfigureEFDbContext
{public interface IEntityFrameworkProviderConnectionOptions : IDisposableObject{bool UseConnectionString { get; }string GetConnectionString();DbConnection GetConnection();}public abstract class EntityFrameworkProviderConnectionOptions : DisposableObject,IEntityFrameworkProviderConnectionOptions{public abstract bool UseConnectionString { get; }public virtual DbConnection GetConnection() => null;public virtual string GetConnectionString() => null;}public class SqlServerProviderConnectionOptions : EntityFrameworkProviderConnectionOptions{private readonly ConnectionStringsOptions _options;public SqlServerProviderConnectionOptions(IOptions<ConnectionStringsOptions> options) => _options = options.Value;public override bool UseConnectionString => true;public override string GetConnectionString() =>$"Server={_options.ServerName};Database={_options.DatabaseName};User Id={_options.UserId};Password={_options.Password};MultipleActiveResultSets=True";// Or//public string GetConnectionString() {//    var connectionStringBuilder = new SqlConnectionStringBuilder();//    connectionStringBuilder.DataSource = _options.ServerName;//    connectionStringBuilder.DataSource = _options.DatabaseName;//    connectionStringBuilder.UserID = _options.UserId;//    connectionStringBuilder.Password = _options.Password;//    connectionStringBuilder.MultipleActiveResultSets = true;//    return connectionStringBuilder.ConnectionString;//}}public class SqliteProviderConnectionOptions : EntityFrameworkProviderConnectionOptions{private readonly ConnectionStringsOptions _options;public SqliteProviderConnectionOptions(IOptions<ConnectionStringsOptions> options) => _options = options.Value;public override bool UseConnectionString => true;//If _options.InMemory then Data Source=InMemorySample;Mode=Memory;Cache=Sharedpublic override string GetConnectionString() =>$"Data Source={_options.DatabaseName};Cache=Shared;";}public class SqliteInMemoryProviderConnectionOptions :EntityFrameworkProviderConnectionOptions{private readonly DbConnection _connection;public SqliteInMemoryProviderConnectionOptions() =>_connection = new SqliteConnection("Data Source=:memory:;Cache=Shared;");public override bool UseConnectionString => false;public override DbConnection GetConnection(){if (_connection.State != System.Data.ConnectionState.Open){_connection.Open();}return _connection;}protected override void Dispose(bool disposing){_connection.Dispose();base.Dispose(disposing);}}public class InMemoryProviderConnectionOptions : EntityFrameworkProviderConnectionOptions{private readonly ConnectionStringsOptions _options;public InMemoryProviderConnectionOptions(IOptions<ConnectionStringsOptions> options) => _options = options.Value;public override bool UseConnectionString => true;public override string GetConnectionString() => _options.DatabaseName;}
}

完成此方案后，我们必须在Startup类中注入“依赖注入”中的所有类。您会在这里注意到，我们添加到Startup类中的所有新方法都是virtual方法。这是为了使此类在MSTest单元测试的集成测试应用程序中可重写，我们将在以后添加。

using ConfigureEFDbContext.Options;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;namespace ConfigureEFDbContext
{public class Startup{public Startup(IConfiguration configuration, IWebHostEnvironment hostEnvironment){Configuration = configuration;HostEnvironment = hostEnvironment;}public IConfiguration Configuration { get; }public IWebHostEnvironment HostEnvironment { get; }// This method gets called by the runtime. Use this method to add services// to the container.public virtual void ConfigureServices(IServiceCollection services){this.AddLogging(services).AddApplicationOptions(services).AddDbContextConfigurerFactory(services).AddEFProviderConnectionOptions(services).AddDbContextConfigurer(services).AddDbContext(services);services.AddControllers();}// This method gets called by the runtime. Use this method to configure// the HTTP request pipeline.public virtual void Configure(IApplicationBuilder app){if (HostEnvironment.IsDevelopment()){app.UseDeveloperExceptionPage();}app.UseHttpsRedirection().UseRouting().UseAuthorization().UseEndpoints(endpoints => endpoints.MapControllers());}//  To use fluent setting we return same objectsprotected virtual Startup AddLogging(IServiceCollection services){services.AddLogging(builder =>builder.AddConfiguration(Configuration.GetSection("Logging")).AddConsole().AddDebug());return this;}//  To use fluent setting we return same objectsprotected virtual Startup AddApplicationOptions(IServiceCollection services){services.AddOptions().Configure<EntityFrameworkOptions>(Configuration.GetSection(EntityFrameworkOptions.KEY_NAME)).Configure<ConnectionStringsOptions>(Configuration.GetSection(ConnectionStringsOptions.KEY_NAME));return this;}protected virtual Startup AddDbContextConfigurerFactory(IServiceCollection services){services.AddSingleton<IDbContextConfigurerFactory,CacheableDbContextConfigurerFactory>();return this;}protected virtual Startup AddEFProviderConnectionOptions(IServiceCollection services){services.AddSingleton<IEntityFrameworkProviderConnectionOptions,SqlServerProviderConnectionOptions>();return this;}protected Startup AddDbContextConfigurer(IServiceCollection services){services.AddSingleton(serviceProvider =>serviceProvider.GetService<IDbContextConfigurerFactory>().GetConfigurer());return this;}protected virtual Startup AddDbContext(IServiceCollection services){AddDbContextPool<DbContext_1>(services);AddDbContextPool<DbContext_2>(services);AddDbContextPool<DbContext_3>(services);// Interface Segregation Principle (ISP)services.AddScoped<IDbContext_1>(provider => provider.GetService<DbContext_1>());services.AddScoped<IDbContext_2>(provider => provider.GetService<DbContext_2>());services.AddScoped<IDbContext_3>(provider => provider.GetService<DbContext_3>());return this;}private Startup AddDbContextPool<TContext>(IServiceCollection services)where TContext : DbContext{services.AddDbContextPool<TContext>((serviceProvider, dbContextOptionsBuilder) =>serviceProvider.GetService<IDbContextConfigurer>().Configure(serviceProvider, dbContextOptionsBuilder));return this;}}
}

最后，我们将添加我们在讨论中使用的DbContext，这是这种类型的类的最简单的标识形式。

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;namespace ConfigureEFDbContext
{//  Interface Segregation Principle (ISP) or Encapsulationpublic interface IDbContext{/// <summary>/// Provides access to database related information and operations for this context./// </summary>DatabaseFacade Database { get; }}public interface IDbContext_1 : IDbContext { }public interface IDbContext_2 : IDbContext { }public interface IDbContext_3 : IDbContext { }public class DbContext_1 : DbContext, IDbContext_1{public DbContext_1(DbContextOptions<DbContext_1> options) : base(options) { }}public class DbContext_2 : DbContext, IDbContext_2{public DbContext_2(DbContextOptions<DbContext_2> options) : base(options) { }}public class DbContext_3 : DbContext, IDbContext_3{public DbContext_3(DbContextOptions<DbContext_3> options) : base(options) { }}
}

在这里，我们将添加一个控制器，以便我们对该场景进行简单测试。

using System.Collections.Generic;
using Microsoft.AspNetCore.Mvc;namespace ConfigureEFDbContext.Controllers
{[ApiController][Route("[controller]")]public class DbContextsController : ControllerBase{private readonly IDbContext_1 _dbContext_1;private readonly IDbContext_2 _dbContext_2;private readonly IDbContext_3 _dbContext_3;public DbContextsController(IDbContext_1 dbContext_1,IDbContext_2 dbContext_2, IDbContext_3 dbContext_3){_dbContext_1 = dbContext_1;_dbContext_2 = dbContext_2;_dbContext_3 = dbContext_3;}[HttpGet]public IEnumerable<string> Get() => new[] {_dbContext_1.Database.ProviderName,_dbContext_2.Database.ProviderName,_dbContext_3.Database.ProviderName};}
}

用Postman测试程序后，我们将得到以下结果：

{"EntityFrameworkOptions": {"Provider": "IN-MEMOR","CanMigrate": false//"Provider": "SQLITE",//"CanMigrate": true},"ConnectionStringsOptions": {"ServerName": null,"DatabaseName": "DEV-V1.db","UserId": null,"Password": null}
}

集成测试

using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;namespace ConfigureEFDbContext.MSUnitTest
{public class IntegrationStartup : Startup{public override void ConfigureServices(IServiceCollection services){base.ConfigureServices(services);services.AddMvc().AddApplicationPart(typeof(Startup).Assembly);}public IntegrationStartup(IConfiguration configuration,IWebHostEnvironment environment) : base(configuration, environment) { }/** ************************************************************************************* We have to choose the correct Provider according to the settings that we put in* the configuration 'integration-settings.json' file, Section 'EntityFrameworkOptions'* *************************************************************************************/// FOR EntityFrameworkProviders.SQLite//protected override Startup AddEFProviderConnectionOptions//                   (IServiceCollection services)//{//    services.AddSingleton<IEntityFrameworkProviderConnectionOptions,//    SqliteProviderConnectionOptions>();//    return this;//}// FOR EntityFrameworkProviders.SQLite but in memory db.//protected override //          Startup AddEFProviderConnectionOptions(IServiceCollection services)//{//    services.AddSingleton<IEntityFrameworkProviderConnectionOptions,//    SqliteInMemoryProviderConnectionOptions>();//    return this;//}// FOR EntityFrameworkProviders.InMemorprotected override Startup AddEFProviderConnectionOptions(IServiceCollection services){services.AddSingleton<IEntityFrameworkProviderConnectionOptions,InMemoryProviderConnectionOptions>();return this;}}
}

运行此测试所需的类。

using System;
using System.IO;
using System.Reflection;namespace ConfigureEFDbContext.MSUnitTest
{public static class Helper{public static string GetParentProjectPath(){var parentProjectName = typeof(Startup).GetTypeInfo().Assembly.GetName().Name;var parentProjectFullName = $"{parentProjectName}.csproj";var applicationBasePath = Directory.GetCurrentDirectory();var directoryInfo = new DirectoryInfo(Directory.GetCurrentDirectory());while (directoryInfo != null){var projectDirectoryInfo = new DirectoryInfo(directoryInfo.FullName);var parentProjectPath = Path.Combine(projectDirectoryInfo.FullName,parentProjectName, parentProjectFullName);if (projectDirectoryInfo.Exists && new FileInfo(parentProjectPath).Exists){return Path.Combine(projectDirectoryInfo.FullName, parentProjectName);}directoryInfo = directoryInfo.Parent;}throw new Exception($"Th parent project {parentProjectName}could not be located using the current application root {applicationBasePath}.");}}
}

通过从WebApplicationFactory继承创建独立于测试类的IntegrationWebApplicationFactory类。

using System.IO;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc.Testing;
using Microsoft.AspNetCore.TestHost;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;namespace ConfigureEFDbContext.MSUnitTest.Fixtures
{public class IntegrationWebApplicationFactory : WebApplicationFactory<Startup>{protected override IWebHostBuilder CreateWebHostBuilder() =>WebHost.CreateDefaultBuilder<IntegrationStartup>(null);protected override void ConfigureWebHost(IWebHostBuilder builder){var contentRoot = Helper.GetParentProjectPath();builder.ConfigureAppConfiguration(config =>{var projectDir = Directory.GetCurrentDirectory();var integrationSettingsPath =Path.Combine(projectDir, "integration-settings.json");var integrationConfig = new ConfigurationBuilder().SetBasePath(contentRoot).AddJsonFile(integrationSettingsPath, false).Build();config.AddConfiguration(integrationConfig);}).UseContentRoot(contentRoot).UseEnvironment("Development").UseStartup<IntegrationStartup>();// Here we can also write our own settings// this called after the 'ConfigureServices' from the Startup// But this is not desirable because we will hide the dependencies// and break the Single Responsibility Principle (SRP).// builder.ConfigureServices(services => {});// Orbuilder.ConfigureTestServices(services =>{//services//   .AddMvc()//   .AddApplicationPart(typeof(Startup).Assembly);});base.ConfigureWebHost(builder);}}
}

一个类来测试我们的控制器类，以确保一切正常。

using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;
using ConfigureEFDbContext.MSUnitTest.Fixtures;
using Microsoft.Extensions.Configuration;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Newtonsoft.Json;namespace ConfigureEFDbContext.MSUnitTest
{[TestClass]public class DbContextsControllerTest{protected static IntegrationWebApplicationFactory _fixture;protected static HttpClient _client;protected readonly IConfiguration _configuration;/// <summary>/// Executes once for the test class. (Optional)/// </summary>[ClassInitialize]public static void TestFixtureSetup(TestContext context){_fixture = new IntegrationWebApplicationFactory();_client = _fixture.CreateClient();_client.BaseAddress = new Uri("http://localhost:60128");_client.DefaultRequestHeaders.Accept.Clear();_client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));}/// <summary>/// Runs before each test. (Optional)/// </summary>[TestInitialize]public void Setup() { }/// <summary>/// Runs once after all tests in this class are executed. (Optional)/// Not guaranteed that it executes instantly after all tests from the class./// </summary>[ClassCleanup]public static void TestFixtureTearDown(){_client.Dispose();_fixture.Dispose();}/// <summary>/// Runs after each test. (Optional)/// </summary>[TestCleanup]public void TearDown() { }[TestMethod]public async Task DbContexts__Should_Initialized(){/** ===== ===== ===== ===== ===== ===== ===== ===== ===== =====* Arrange* this is where you would typically prepare everything for the test,* in other words, prepare the scene for testing* (creating the objects and setting them up as necessary)* ===== ===== ===== ===== ===== ===== ===== ===== ===== =====*/var requestUri = new Uri("/DbContexts", UriKind.Relative);/** ===== ===== ===== ===== ===== ===== ===== ===== ===== =====* Act* this is where the method we are testing is executed.* ===== ===== ===== ===== ===== ===== ===== ===== ===== =====*/var response = await _client.GetAsync(requestUri).ConfigureAwait(false);var responseBody = await response.Content.ReadAsStringAsync().ConfigureAwait(false);response.EnsureSuccessStatusCode();var result = JsonConvert.DeserializeObject<List<string>>(responseBody);/** ===== ===== ===== ===== ===== ===== ===== ===== ===== =====* Assert* This is the final part of the test where we compare what we expect* to happen with the actual result of the test method execution.* ===== ===== ===== ===== ===== ===== ===== ===== ===== =====*/Assert.IsNotNull(result);}}
}

结论