AddDbContext was called with configuration, but the context type 'MyDBContext' only declares a parameterless constructor

 

System.ArgumentException
  HResult=0x80070057
  Message=AddDbContext was called with configuration, but the context type 'MyDBContext' only declares a parameterless constructor. 
  This means that the configuration passed to AddDbContext will never be used. 
  If configuration is passed to AddDbContext, then 'MyDBContext' should declare a constructor that accepts a DbContextOptions<MyDBContext> and must pass it to the base constructor for DbContext.
  Source=Microsoft.EntityFrameworkCore
  StackTrace:
   at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.CheckContextConstructors[TContext]()
   at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.AddDbContext[TContextService,TContextImplementation](IServiceCollection serviceCollection, Action`2 optionsAction, ServiceLifetime contextLifetime, ServiceLifetime optionsLifetime)
   at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.AddDbContext[TContextService,TContextImplementation](IServiceCollection serviceCollection, Action`1 optionsAction, ServiceLifetime contextLifetime, ServiceLifetime optionsLifetime)
   at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.AddDbContext[TContext](IServiceCollection serviceCollection, Action`1 optionsAction, ServiceLifetime contextLifetime, ServiceLifetime optionsLifetime)
   at WebApi1.Startup.ConfigureServices(IServiceCollection services) in C:\Users\pxm\source\repos\WebApi1\WebApi1\Startup.cs:line 31
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Microsoft.AspNetCore.Hosting.ConfigureServicesBuilder.InvokeCore(Object instance, IServiceCollection services)
   at Microsoft.AspNetCore.Hosting.ConfigureServicesBuilder.<>c__DisplayClass9_0.<Invoke>g__Startup|0(IServiceCollection serviceCollection)
   at Microsoft.AspNetCore.Hosting.ConfigureServicesBuilder.Invoke(Object instance, IServiceCollection services)
   at Microsoft.AspNetCore.Hosting.ConfigureServicesBuilder.<>c__DisplayClass8_0.<Build>b__0(IServiceCollection services)
   at Microsoft.AspNetCore.Hosting.GenericWebHostBuilder.UseStartup(Type startupType, HostBuilderContext context, IServiceCollection services)
   at Microsoft.AspNetCore.Hosting.GenericWebHostBuilder.<>c__DisplayClass12_0.<UseStartup>b__0(HostBuilderContext context, IServiceCollection services)
   at Microsoft.Extensions.Hosting.HostBuilder.CreateServiceProvider()
   at Microsoft.Extensions.Hosting.HostBuilder.Build()
   at WebApi1.Program.Main(String[] args) in C:\Users\pxm\source\repos\WebApi1\WebApi1\Program.cs:line 16

 

翻译：

已使用配置调用AddDbContext，但上下文类型“MyDBContext”仅声明一个无参数构造函数。这意味着传递给AddDbContext的配置将永远不会被使用。
如果将配置传递给AddDbContext，那么“MyDBContext”应该声明一个接受DbContextOptions<MyDBContext>的构造函数，并且必须将其传递给DbContext的基本构造函数。

 

解决方法：

MyDBContext添加一个DbContextOptions<MyDBContext>类型参数的构造函数