EF Core 3.1.8 - Migrations Error - No database provider has been configured for this DbContext

Question

I'm trying to add migrations and receiving the following error:

Build started...
Build succeeded.
System.InvalidOperationException: No database provider has been configured for this DbContext. A provider can be configured by overriding the DbContext.OnConfiguring method or by using AddDbContext on the application service provider. If AddDbContext is used, then also ensure that your DbContext type accepts a DbContextOptions<TContext> object in its constructor and passes it to the base constructor for DbContext.
   at Microsoft.EntityFrameworkCore.Internal.DbContextServices.Initialize(IServiceProvider scopedProvider, IDbContextOptions contextOptions, DbContext context)
   at Microsoft.EntityFrameworkCore.DbContext.get_InternalServiceProvider()
   at Microsoft.EntityFrameworkCore.DbContext.Microsoft.EntityFrameworkCore.Infrastructure.IInfrastructure<System.IServiceProvider>.get_Instance()
   at Microsoft.EntityFrameworkCore.Infrastructure.Internal.InfrastructureExtensions.GetService[TService](IInfrastructure`1 accessor)
   at Microsoft.EntityFrameworkCore.Infrastructure.AccessorExtensions.GetService[TService](IInfrastructure`1 accessor)
   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)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType)
   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)
No database provider has been configured for this DbContext. A provider can be configured by overriding the DbContext.OnConfiguring method or by using AddDbContext on the application service provider. If AddDbContext is used, then also ensure that your DbContext type accepts a DbContextOptions<TContext> object in its constructor and passes it to the base constructor for DbContext.

Already tried to add the EntityFrameworkCore.Design package and my constructor is like

public MyContext(DbContextOptions<MyContext> options) : base(options)
{

}

And keep throwing the error:

Unable to create an object of type 'MyContext'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728

Updated with database configuration

obs:

User is a abstract class.
I'm using code first and Migrations not yet exist.

public class MyContext : DbContext
{
    public VenturaContext(DbContextOptions<MyContext> options) : base(options)
    {

    }

    public DbSet<Usuario> Usuarios { get; set; }
    public DbSet<Employee> Employees { get; set; }
    public DbSet<Admin> Administrators { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        //modelBuilder.Entity<User>().ToTable("Users");
        base.OnModelCreating(modelBuilder);
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        base.OnConfiguring(optionsBuilder);
    }
}

[Updated 2 - my simple solution]

Just set my conn string on OnConfiguring method and create a empty constructor on MyContext. That was enough for what was creating.

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {

            if (!optionsBuilder.IsConfigured)
            {
                optionsBuilder.UseSqlServer("Server=KONOHA; Database=my_database; User Id=user; password=********; MultipleActiveResultSets=true");
            }

            base.OnConfiguring(optionsBuilder);
        }

Yes. I'm applying it com startup file on ConfigureServices method. — Alex Santos
It would help if you share the database configuraition as an edit to the question. — MultiValidation
I updated the post and add some observations can be important. — Alex Santos

Yinqiu Yinqiu · Accepted Answer · 2020-10-13T09:55:28

You can see this article.

Configure DBContext via AddDbContext:

services.AddDbContext<MyContext>(options =>
                options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

Then in your MyContext:

public class MyContext : DbContext
{

public MyContext(DbContextOptions<MyContext> options) : base(options)
{
}  
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    
    base.OnModelCreating(modelBuilder);
}
}

appsettings.json:

  "ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=MyContext;Trusted_Connection=True;MultipleActiveResultSets=true"
  }

EF Core 3.1.8 - Migrations Error - No database provider has been configured for this DbContext

1 Answers