Entity Framework Core - Migration - No Parameterless Constructor Defined for this Object

Question

I am working with the latest .Net Core and EF Core in Visual Studio 2017. I have created a model and it was working great. I have since made some modifications and am gett

Answer 1

Design-time tools attempt to automatically find how your application creates instances of your DbContext type. If EF cannot find a suitable way to initialize your DbContext, you may encounter this error.

Options: 1- Either create a parameterless constructor

  public AlmanacDb() { }
  protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
  {           
       optionsBuilder.UseSqlServer(_connString);
  }

  private readonly string _connString = "";

2-

public AlmanacDb Create()
{
     var optionsBuilder = new DbContextOptionsBuilder();
     optionsBuilder.UseSqlServer(connectionString);

     return new AlmanacDb(optionsBuilder.Options);
}

https://docs.microsoft.com/en-us/ef/core/miscellaneous/configuring-dbcontext