Asp.net core error: Unable to create an object of type 'ApplicationDBContext'.
Dung Do Tien
May 30 2021
358
When working with FE core, I have created a ApplicationDBContext inherited from DbContext:
using System;
using Domain;
using Microsoft.EntityFrameworkCore;
namespace Persistence
{
public class ApplicationDBContext: DbContext
{
public ApplicationDBContext(DbContextOptions options) : base(options){}
public DbSet<Student> Students { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlServer(
@"Data Source=(localdb)\MSSQLLocalDB;Initial Catalog=test123;Integrated Security=True");
}
}
}
when I running command to help migrations database
dotnet ef migrations add initcreate -s ..\API\
But I got an error:
Unable to create an object of type 'ApplicationDBContext'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728
Please tell me how can I resolve it?
Have 3 answer(s) found.
-
d1
dang thanh tuan May 30 2021
When you move your DbContext to another project you should do this:
if you use visual studio:
right-click on your main project and choose "Set as startup project"
then run tools > NuGet package manager > package manager console
make sure you have chosen the project which contains your DbContext (from drop-down list)
and run:Add-Migration .....if you use
dotnet-clijust type this in terminal:dotnet ef migrations add MigrationName -s mainProject -p DbContextProject
make sure in the terminal you are in the directory which contains both main and
DbContextproject -
M-9
Mahery Andriniaina Razafimanantsoa May 30 2021
You get that error because to generate migrations you need either:
Solution 1: A
DbContextwith a default constructor (that is, a parameterless constructor)Solution 2: Being able to get the
DbContextfrom ApplicationServices (that is, Dependency Injection)Solution 3: A design-time factory that returns a properly configured
DbContext.Hope this helps you!
-
D-11
Dorian G. Ramos May 30 2021
Solution for someone who has multiple projects:
I had the same issue and solved it by selecting one project as a startup project instead of multiple projects.
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