无法使用Entity Framework创建迁移脚本

Question

(neither of the online resources helped, so I am creating a new thread.)

I am confused with errors I receive when running the following command to create migration scripts:

dotnet ef migrations add InitialCreate -v

I receive the following error when I have parameterless constructor for my dbcontext:

No database provider has been configured for this DbContext.

and when I remove the parameterless constructor, it complains I should put it back:

No parameterless constructor defined for this object

I define the dbcontext as:

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

    }

    public DbSet<Item> Tools { set; get; }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        builder.ApplyConfiguration(new ToolItemEntityTypeConfiguration());
    }
}

The Service is defined as:

public IServiceProvider ConfigureServices(IServiceCollection services)
{
    services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
    services.AddCustomDbContext(Configuration);

    var container = new ContainerBuilder();
    container.Populate(services);
    return new AutofacServiceProvider(container.Build());
}

...

public static class CustomExtensionMethods
{
    public static IServiceCollection AddCustomDbContext(this IServiceCollection services, IConfiguration configuration)
    {
        services.AddDbContext<ItemContext>(options =>
        {
            options.UseSqlServer(configuration.GetConnectionString("DefaultConnection"),
                                    sqlServerOptionsAction: sqlOptions =>
                                    {
                                        sqlOptions.MigrationsAssembly(typeof(Startup).GetTypeInfo().Assembly.GetName().Name);
                                        sqlOptions.EnableRetryOnFailure(maxRetryCount: 10, maxRetryDelay: TimeSpan.FromSeconds(30), errorNumbersToAdd: null);
                                    });
            options.ConfigureWarnings(warnings => warnings.Throw(RelationalEventId.QueryClientEvaluationWarning));
        });
        return services;
    }
}

Answer 1

I think this line of code

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

}

Should change to

public ItemContext(DbContextOptions options) : base(options)
{

}

If this doesnt work for you try to register this in your Startup.cs

services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();