无法创建类型为 '[DBContext名称]' 的对象。针对设计时所支持的不同模式进行操作。

我正在Udemy上学习Mosh Hamedani的ASP.NET MVC课程。

在使用代码优先（Entity Framework）设计我的数据库时，我遇到了一个错误。

起初，我遇到了"未在程序集中找到DbContext"的错误。解决了这个问题后，另一个错误突然出现了。

下面的图片将展示您在添加迁移时发现的错误。我已经搜索过相同的错误，但徒劳无功。我已经苦苦挣扎了两个小时，但到目前为止什么都没解决。

请有人帮帮我。谢谢

无法创建类型为'Vidly_Context'的对象。有关设计时支持的不同模式，请参见https://go.microsoft.com/fwlink/?linkid=851728。

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在添加自己的DbContext构造函数（带有两个参数）后出现了类似的问题。应用程序是正常的，但迁移停止工作。 通过使用Dotnet工具@xspdf提供的信息更新EF（在使用5时使用3.1.5的奇怪原因），并将提到的构造函数替换为方法+硬编码的默认连接字符串（如果未设置）来修复。

dotnet tool update --global dotnet-ef

// following command show the most during migration build/run in cmd
// mind current dir is Migrations folder of (VS) startup project here
dotnet ef --startup-project ../ --verbose migrations add test

3.1.5 & 上下文激活错误

The Entity Framework tools version '3.1.5' is older than that of the runtime '5.0.0'. Update the tools for the latest features and bug fixes.
Finding DbContext classes...
Finding IDesignTimeDbContextFactory implementations...
Finding application service provider in assembly '...'...
Finding Microsoft.Extensions.Hosting service provider...
No static method 'CreateHostBuilder(string[])' was found on class 'Program'.
No application service provider was found.
Finding DbContext classes in the project...
Found DbContext '...Context'.
Microsoft.EntityFrameworkCore.Design.OperationException: Unable to create an object of type '...Context'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728
 ---> System.InvalidOperationException: Unable to resolve service for type 'System.String' while attempting to activate '...'. (my additional parameter)
   at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.ConstructorMatcher.CreateInstance(IServiceProvider provider)
   at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.CreateInstance(IServiceProvider provider, Type instanceType, Object[] parameters)
   at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetServiceOrCreateInstance(IServiceProvider provider, Type type)
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.<>c__DisplayClass13_4.<FindContextTypes>b__13()
   --- End of inner exception stack trace ---
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.<>c__DisplayClass13_4.<FindContextTypes>b__13()
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(Func`1 factory)
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(String contextType)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType, String namespace)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType, String namespace)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>c__DisplayClass0_0.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Unable to create an object of type '...Context'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728