关于add migration 报错的问题解决方案

• The current CSharpHelper cannot scaffold literals of type 'Microsoft.EntityFrameworkCore.Metadata.Internal.DirectConstructorBinding'. Configure your services to use one that can.

  解决方案：程序包管理控制台->Install-Package Microsoft.EntityFrameworkCore.Design

• Unable to create an object of type 'ActivityDbContext'. Add an implementation of 'IDesignTimeDbContextFactory<ActivityDbContext>' to the project, or see https://go.microsoft.com/fwlink/?linkid=851728 for additional patterns supported at design time.

  修改Program
  before：
  public class Program
      {
          public static void Main(string[] args)
          {
              CreateWebHostBuilder(args).Build().Run();
          }
  
          public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
              WebHost.CreateDefaultBuilder(args)
                  .UseStartup<Startup>();
      }
  
  now：
  
          public static void Main(string[] args)
          {
              BuildWebHost(args).Run();
          }
  
          public static IWebHost BuildWebHost(string[] args) =>
              WebHost.CreateDefaultBuilder(args)
                  .UseStartup<Startup>()
                  .Build();
      }