基于 ASP.NET Core 中的现有数据库创建实体框架模型答案

【问题标题】：Create Entity Framework model based on an existing database in ASP.NET Core基于 ASP.NET Core 中的现有数据库创建实体框架模型
【发布时间】：2017-07-11 13:12:54
【问题描述】：

我正在尝试基于 ASP.NET Core 中的现有数据库创建实体框架模型。我不能让 Scaffold-DbContext 工作！我搜索了 Stackoverflow 和其他网站，看看我的 ASP.NET Core Web 应用程序项目中的包是否不正确，但我仍然无法使其工作。在包管理器控制台中运行 Scaffold-DbContext 时出现以下错误：

PM> Scaffold-DbContext "Server=.;Database=TravelAgency;Trusted_Connection=True;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models
System.AggregateException: Ett eller flera fel har uppstï¿½tt. ---> System.MethodAccessException: Ett fï¿½rsï¿½k av metoden Microsoft.EntityFrameworkCore.Scaffolding.Configuration.Internal.ModelConfiguration.get_EntityConfigurations() 
att komma ï¿½t metoden Microsoft.EntityFrameworkCore.Metadata.Internal.EntityTypeNameComparer..ctor() misslyckades.    vid Microsoft.EntityFrameworkCore.Scaffolding.Configuration.Internal.ModelConfiguration.get_EntityConfigurations()

抱歉，我没有找到在包管理器控制台中用英文显示错误的方法。这是关于 System.AggregateException：发生了一个或多个错误。我的 project.json 文件如下所示：

{
  "buildOptions": {
"emitEntryPoint": true,
"preserveCompilationContext": true
  },
  "dependencies": {
"EntityFramework": "6.1.3",
"Microsoft.AspNetCore.Authentication.Cookies": "1.0.0",
"Microsoft.AspNetCore.Diagnostics": "1.0.0",
"Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore": "1.0.0",
"Microsoft.AspNetCore.Identity.EntityFrameworkCore": "1.0.0",
"Microsoft.AspNetCore.Mvc": "1.0.1",
"Microsoft.AspNetCore.Razor.Tools": {
  "type": "build",
  "version": "1.0.0-preview2-final"
},
"Microsoft.AspNetCore.Routing": "1.0.1",
"Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",
"Microsoft.AspNetCore.Server.Kestrel": "1.0.1",
"Microsoft.AspNetCore.StaticFiles": "1.0.0",
"Microsoft.EntityFrameworkCore": "1.1.0",
"Microsoft.EntityFrameworkCore.Design": "1.0.0-preview2-final",
"Microsoft.EntityFrameworkCore.SqlServer": "1.1.0",
"Microsoft.EntityFrameworkCore.SqlServer.Design": "1.1.0",
"Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final",
"Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0",
"Microsoft.Extensions.Configuration.Json": "1.0.0",
"Microsoft.Extensions.Configuration.UserSecrets": "1.0.0",
"Microsoft.Extensions.Logging": "1.1.0",
"Microsoft.Extensions.Logging.Console": "1.0.0",
"Microsoft.Extensions.Logging.Debug": "1.0.0",
"Microsoft.Extensions.Options.ConfigurationExtensions": "1.0.0",
"Microsoft.VisualStudio.Web.BrowserLink.Loader": "14.0.0",
"Microsoft.VisualStudio.Web.CodeGeneration.Tools": {
  "version": "1.0.0-preview2-final",
  "type": "build"
},
"Microsoft.VisualStudio.Web.CodeGenerators.Mvc": {
  "type": "build",
  "version": "1.0.0-preview2-final"
},
"NuGet.CommandLine": "3.5.0"
  },
  "frameworks": {

"net461": {}

  },

  "publishOptions": {
"include": [
  "wwwroot",
  "**/*.cshtml",
  "appsettings.json",
  "web.config"
]
  },
  "runtimeOptions": {
"configProperties": {
  "System.GC.Server": true
}
  },
  "scripts": {
"prepublish": [ "bower install", "dotnet bundle" ],
"postpublish": [ "dotnet publish-iis --publish-folder %publish:OutputPath% --framework %publish:FullTargetFramework%" ]
  },
  "tools": {
"BundlerMinifier.Core": "2.0.238",
"Microsoft.AspNetCore.Razor.Tools": "1.0.0-preview2-final",
"Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final",
"Microsoft.Extensions.SecretManager.Tools": "1.0.0-preview2-final",
"Microsoft.VisualStudio.Web.CodeGeneration.Tools": {
  "version": "1.0.0-preview2-final",
  "imports": [
    "portable-net45+win8"
  ]
}
  },
  "userSecretsId": "aspnet-TravelAgencyApplication-3fa3cffa-93a0-470d-b08a-145e604eb5f7"
}

提前致谢！最好的问候，阿提拉

【问题讨论】：

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

【解决方案1】：

您应该尝试运行以下命令。

Scaffold-DbContext "Server=(localdb)\mssqllocaldb;Database=Blogging;Trusted_Connection=True;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models

Here is the official documentation on reverse engineering a db into your models. Make sure you have the correct packages installed per this link.

【讨论】：

感谢 destructi6n，但您的意思是我应该创建一个本地数据库才能使其正常工作吗？我之前创建了一个 Sql Server 2012 数据库，但我似乎无法让 Scaffold-DbContext 工作，即使我使用了你提到的命令。
您应该做的是将我的连接字符串（即 Server=(localdb)\mssqllocaldb;Database=Blogging;Trusted_Connection=True;）替换为指向您的数据库的连接字符串。我之前在我的 localdb 实例中使用过这个命令。如果你提供你的连接字符串，这个命令应该对你有用。

【解决方案2】：

在包管理器控制台中使用 .net core 进行这项工作时，我遇到了很多问题。我结束了从命令行发出命令，我在这方面取得了更大的成功。请参阅此处了解如何执行此操作：https://docs.microsoft.com/en-us/ef/core/miscellaneous/cli/dotnet。

例如，从您的项目目录运行以下命令：

dotnet ef dbcontext scaffold "Server=YourServer;Database=YourDb;Integrated Security=True;" Microsoft.EntityFrameworkCore.SqlServer --output-dir Models

此处列出了一个问题，现已关闭，但我似乎仍有问题：https://github.com/aspnet/EntityFramework/issues/5376

【讨论】：

【解决方案3】：

谢谢大家！我不知道我到底做了什么，但我终于用 Scaffold-DbContext 命令成功了：

Scaffold-DbContext "Server=DATOR;Database=TravelAgency;Trusted_Connection=True;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models

这是 destructi6n 描述的命令，已针对我的 SQL Server 2012 数据库进行了调整。现在我的 project.json 文件看起来像这样：

{
  "buildOptions": {
"emitEntryPoint": true,
"preserveCompilationContext": true
  },
  "dependencies": {
"EntityFramework": "6.1.3",
"Microsoft.AspNetCore.Authentication.Cookies": "1.0.0",
"Microsoft.AspNetCore.Diagnostics": "1.0.0",
"Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore": "1.0.0",
"Microsoft.AspNetCore.Identity.EntityFrameworkCore": "1.0.0",
"Microsoft.AspNetCore.Mvc": "1.0.1",
"Microsoft.AspNetCore.Razor.Tools": {
  "type": "build",
  "version": "1.0.0-preview2-final"
},
"Microsoft.AspNetCore.Routing": "1.0.1",
"Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",
"Microsoft.AspNetCore.Server.Kestrel": "1.0.1",
"Microsoft.AspNetCore.StaticFiles": "1.0.0",
"Microsoft.EntityFrameworkCore": "1.1.0",
"Microsoft.EntityFrameworkCore.Design": "1.1.0",
"Microsoft.EntityFrameworkCore.SqlServer": "1.1.0",
"Microsoft.EntityFrameworkCore.SqlServer.Design": "1.1.0",
"Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final",
"Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0",
"Microsoft.Extensions.Configuration.Json": "1.0.0",
"Microsoft.Extensions.Configuration.UserSecrets": "1.0.0",
"Microsoft.Extensions.Logging": "1.1.0",
"Microsoft.Extensions.Logging.Console": "1.0.0",
"Microsoft.Extensions.Logging.Debug": "1.0.0",
"Microsoft.Extensions.Options.ConfigurationExtensions": "1.0.0",
"Microsoft.VisualStudio.Web.BrowserLink.Loader": "14.0.0",
"Microsoft.VisualStudio.Web.CodeGeneration.Tools": {
  "version": "1.0.0-preview2-final",
  "type": "build"
},
"Microsoft.VisualStudio.Web.CodeGenerators.Mvc": {
  "type": "build",
  "version": "1.0.0-preview2-final"
},
"NuGet.CommandLine": "3.5.0"
  },
  "frameworks": {

"net461": {}

  },

  "publishOptions": {
"include": [
  "wwwroot",
  "**/*.cshtml",
  "appsettings.json",
  "web.config"
]
  },
  "runtimeOptions": {
"configProperties": {
  "System.GC.Server": true
}
  },
  "scripts": {
"prepublish": [ "bower install", "dotnet bundle" ],
"postpublish": [ "dotnet publish-iis --publish-folder %publish:OutputPath% --framework %publish:FullTargetFramework%" ]
  },
  "tools": {
"BundlerMinifier.Core": "2.0.238",
"Microsoft.AspNetCore.Razor.Tools": "1.0.0-preview2-final",
"Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final",
"Microsoft.Extensions.SecretManager.Tools": "1.0.0-preview2-final",
"Microsoft.VisualStudio.Web.CodeGeneration.Tools": {
  "version": "1.0.0-preview2-final",
  "imports": [
    "portable-net45+win8"
  ]
}
  },
  "userSecretsId": "aspnet-TravelAgencyApplication-3fa3cffa-93a0-470d-b08a-145e604eb5f7"
}

亲切的问候，阿提拉

【讨论】：