配置EntityFramework Core时的依赖注入异常答案

【问题标题】：Dependency-injection Exception when configuring EntityFramework Core配置EntityFramework Core时的依赖注入异常
【发布时间】：2016-09-24 05:49:53
【问题描述】：

//the Startup.cs file configuration settings.
public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();
    services.AddEntityFramework().AddSqlServer().AddDbContext<PortContext>();
}

project.json

 {
  "dependencies": {
  "Microsoft.NETCore.App": {
  "version": "1.0.0",
  "type": "platform"
 },
  "Microsoft.EntityFrameworkCore.Design": {
  "version": "1.0.0-*",
  "type": "build"
 },
  "Microsoft.AspNetCore.Diagnostics": "1.0.0",
  "Microsoft.AspNetCore.Mvc": "1.0.0",
  "Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",
  "Microsoft.AspNetCore.Server.Kestrel": "1.0.0",
  "Microsoft.Extensions.Logging.Console": "1.0.0",
  "Microsoft.AspNetCore.StaticFiles": "1.0.0",
  "MailKit": "1.3.0-beta7",
  "Microsoft.Extensions.Configuration.Json": "1.0.0",
  "EntityFramework.Core": "7.0.0-rc1-final",
  "EntityFramework.MicrosoftSqlServer": "7.0.0-rc1-final",
  "mongocsharpdriver": "2.3.0-rc1",
  "Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final"
 },

"tools": {
  "Microsoft.AspNetCore.Server.IISIntegration.Tools": "1.0.0-preview2-final",
  "Microsoft.AspNetCore.Razor.Tools": {
  "version": "1.0.0-preview1-final",
  "imports": "portable-net45+win8+dnxcore50"
},
  "Microsoft.EntityFrameworkCore.Tools": "1.0.0-*"
},
"commands": {
"ef": "EntityFramework.Commands"
},
"frameworks": {
"netcoreapp1.0": {
  "imports": [
    "dotnet5.6",
    "portable-net45+win8"
  ]
 }
},

 "buildOptions": {
 "emitEntryPoint": true,
 "preserveCompilationContext": true
},

"runtimeOptions": {
 "configProperties": {
   "System.GC.Server": true
 }
},

"publishOptions": {
 "include": [
   "wwwroot",
   "web.config"
 ]
},

"scripts": {
"postpublish": [ "dotnet publish-iis --publish-folder %publish:OutputPath% --framework %publish:FullTargetFramework%" ]
 }
}

    And my PortContext.cs file's OnConfiguring method is given below.

    protected override void OnConfiguring(DbContextOptionsBuilder options)
    {
        var connString =Startup.Configuration["Data:PortContextConnection"];
        options.UseSqlServer(connString);
        base.OnConfiguring(options);
    }

当我运行 dotnet ef migrations add 命令时出现异常：

在启动类“WebApplication8.Startup”上调用方法“ConfigureServices”时出错。考虑使用 IDbContextFactory 在设计时覆盖 DbContext 的初始化。错误：无法从程序集“Microsoft.Extensions.DependencyInjection.Abstractions, Version=1.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60”中加载类型“Microsoft.Extensions.DependencyInjection.ServiceCollectionExtensions”。

谁能帮我解决这个问题？

【问题讨论】：

它明确表示IDbContextFactory 依赖未注册。你也可以分享你的 DbContext 文件吗？
感谢您的回复。而 PortContext 文件是从 DbContext 文件派生的。来自 Microsoft.Data.Entity 的 DbContext 文件。在 PortContext 文件中，只有上面的 OnConfiguring 方法的表定义。
试试services.AddDbContext<PortContext>(options => options.UseSqlServer(configuration["connectionstring path"], b => b.MigrationAssembly("host project namespace"))); 你需要安装Microsoft.EntityFrameworkCore 包。
谢谢，我也试过了，但 MigrationAssembly 无法识别。我不得不改用 MigrationsAssembly。
而且问题还没有解决，还在寻找解决方案。这是由于 .net core 的版本造成的吗？

标签： c# asp.net-core .net-core asp.net-core-mvc entity-framework-core

【解决方案1】：

我终于找到了解决办法。当我们使用 project.json 的多个不匹配版本的包时会出现此问题。（主要是 rc1 或 rc2 版本）。我已经重新排列了 project.json 依赖项，问题已经解决了。

  "dependencies": {
//"EntityFramework.Core": "7.0.0-rc1-final",
//"EntityFramework.MicrosoftSqlServer": "7.0.0-rc1-final",
"MailKit": "1.3.0-beta7",
//"EntityFramework.Core": "7.0.0-rc1-final",
"Microsoft.NETCore.App": {
  "version": "1.0.0",
  "type": "platform"
},
"Microsoft.AspNetCore.Mvc": "1.0.0",
"Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",
"Microsoft.AspNetCore.Server.Kestrel": "1.0.0",
"Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0",
"Microsoft.Extensions.Configuration.FileExtensions": "1.0.0",
"Microsoft.Extensions.Configuration.Json": "1.0.0",
"Microsoft.Extensions.Logging": "1.0.0",
"Microsoft.Extensions.Logging.Console": "1.0.0",
"Microsoft.Extensions.Logging.Debug": "1.0.0",
//"Microsoft.Extensions.Configuration.UserSecrets": "1.0.0",
"Microsoft.EntityFrameworkCore": "1.0.0",
//"MyLibrary": "1.0.0-*",
"Microsoft.EntityFrameworkCore.SqlServer": "1.0.0",
"Microsoft.AspNetCore.StaticFiles": "1.0.0",
"Microsoft.AspNetCore.Diagnostics": "1.0.0",
"Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final",
//"OpenIddict": "1.0.0-alpha2-0331",
"Microsoft.EntityFrameworkCore.Design": {
  "version": "1.0.0-*",
  "type": "build"
},
//"EntityFramework.SqlServer": "7.0.0-beta7"

您可以看到我已经从 project.json 中删除了所有 rc1 和 rc2 版本。NET 核心版本正在快速更新。我认为我们需要通过仅使用一组更新而不是混合所有更新来管理我们的代码。感谢所有回复的人。

【讨论】：