AddDbContext was called with configuration, but the context type 'MyContext' only declares a parameterless constructor?

.net-core c# entity-framework entity-framework-core

Question

In the following console application (.Net core 2.0), the scaffold-dbcontext created the following DbContext

public partial class MyContext : DbContext
{
    public virtual DbSet<Tables> Tables { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        if (!optionsBuilder.IsConfigured) { optionsBuilder.UseSqlServer(Program.Conn); }
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder) { .... }
}

In the Main() (static void Main(string[] args)), the following code

var services = new ServiceCollection();
var conn = configuration.GetConnectionString("MySource");
services.AddDbContext<MyContext>(o => o.UseSqlServer(conn)); // Error

got the following run-time error?

AddDbContext was called with configuration, but the context type 'MyContext' only declares a parameterless constructor. This means that the configuration passed to AddDbContext will never be used

1
40
8/29/2017 8:25:43 PM

Accepted Answer

As the error said it if you configure your MyContext through AddDbContext then you need too add a constructor that receive a parameter of type DbContextOptions<MyContext> into your MyContext class like below

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

If you don't do that, ASP.Net Core will not be able to inject the configuration you set with AddDbContext.

74
8/29/2017 8:48:22 PM


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