Scaffold-DbContext 失败。 System.TypeLoadException：无法在 .NET Core 上加载类型“Microsoft.EntityFrameworkCore.Internal.ProductInfo”

Question

我刚刚创建了一个 ASP .NET Core 3.1 API Web 应用程序，并想从我的 Oracle 数据库生成“DbContext”文件。 我很失望地发现似乎没有像 .NET Standard 那样内置的视觉设计器。

我尝试过的：

• 创建了 .NET Core 3.1 API Web 应用程序。
• 安装了以下 NuGet 包：
  • Microsoft.EntityFrameworkCore 3.1.2；
  • Microsoft.EntityFrameworkCore.Design 2.2.6；
  • Microsoft.EntityFrameworkCore.Relational 2.2.6；
  • Microsoft.EntityFrameworkCore.Relational.Design 1.1.6
  • Microsoft.EntityFrameworkCore.Tools 2.2.6；
  • Oracle.EntityFrameworkCore 2.19.6；
  • Oracle.ManagedDataAccess.Core 2.19.6；

然后我尝试在包管理器控制台上调用Scaffold-DbContext命令：

Scaffold-DbContext "DATA SOURCE=(DESCRIPTION=(SOURCE_ROUTE=OFF)(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=myHostName)(PORT=myPortNumber)))(CONNECT_DATA=(SID=mySID)(SERVER=DEDICATED))); User ID=myID;Password=myPassword;" Oracle.ManagedDataAccess -OutputDir Models -Tables myTableName

使用此命令，我希望为我的表生成一个 db 上下文类，但是，返回以下错误：

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> System.TypeLoadException: Could not load type 'Microsoft.EntityFrameworkCore.Internal.ProductInfo' from assembly 'Microsoft.EntityFrameworkCore, Version=3.1.2.0, Culture=neutral, PublicKeyToken=adb9793829ddae60'.
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor..ctor(Object reportHandler, IDictionary args)
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture)
   at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
   at System.Activator.CreateInstance(Type type, Object[] args)
   at Microsoft.EntityFrameworkCore.Tools.ReflectionOperationExecutor..ctor(String assembly, String startupAssembly, String projectDir, String dataDirectory, String rootNamespace, String language)
   at Microsoft.EntityFrameworkCore.Tools.Commands.ProjectCommandBase.CreateExecutor()
   at Microsoft.EntityFrameworkCore.Tools.Commands.DbContextScaffoldCommand.Execute()
   at Microsoft.EntityFrameworkCore.Tools.Commands.CommandBase.<>c__DisplayClass0_0.<Configure>b__0()
   at Microsoft.DotNet.Cli.CommandLine.CommandLineApplication.Execute(String[] args)
   at Microsoft.EntityFrameworkCore.Tools.Program.Main(String[] args)
Exception has been thrown by the target of an invocation.

Answer 1

分两步解决：

1. 所有实体框架和 Microsoft.VisualStudio.Web.CodeGeneration.Design 包必须处于同一版本级别，例如 v3.1 以下

   <PropertyGroup> <OutputType>Exe</OutputType> <TargetFramework>netcoreapp3.1</TargetFramework> </PropertyGroup> <ItemGroup> <PackageReference Include="Hangfire" Version="1.7.11" /> <PackageReference Include="Microsoft.EntityFrameworkCore" Version="3.1" /> <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="3.1" /> <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="3.1" /> <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="3.1" /> </ItemGroup> </Project>

2. 鉴于上述情况，TypeLoadException 应该消失，可能会被Instance Failure错误取代，比如您使用的连接字符串是否与您的项目使用的连接字符串相同。 通过在连接字符串中使用单反斜杠而不是通常的双反斜杠来解决实例故障：

错误道：

Scaffold-DbContext "Server=DESKTOP-C2IEMCJ\\MSSQLSERVER17;Database=HangFire01;Trusted_Connection=True" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models

正确的方式 - 注意下面 MSSQLSERVER17 之前的单斜杠：

Scaffold-DbContext "Server=DESKTOP-C2IEMCJ\MSSQLSERVER17;Database=HangFire01;Trusted_Connection=True" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models