IDesignTimeDbContextFactory without a connection string

[bdovaz]

In other providers such as Microsoft.EntityFrameworkCore.Sqlite or Pomelo.EntityFrameworkCore.MySql, you can implement it by calling UseSqlite() or UseMySql() without parameters.

That is, without connecting to a real database.

With Npgsql.EntityFrameworkCore.PostgreSQL and UseNpgsql(), I get the following error:

Unable to create a 'DbContext' of type 'MyDbContext'. The exception 'The ConnectionString property has not been initialized.' was thrown while attempting to create an instance. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728

Code:

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Design;

public class MybContextContextFactory : IDesignTimeDbContextFactory<MyDbContext>
{
    public MyDbContext CreateDbContext(string[] args)
    {
        DbContextOptionsBuilder<MyDbContext> dbContextOptionsBuilder = new();
        dbContextOptionsBuilder.UseNpgsql();

        return new MyDbContext(dbContextOptionsBuilder.Options);
    }
}

Command:

dotnet ef dbcontext script --output Databas.sql

cc @roji

[roji]

I cannot reproduce this - your code above works as-is for me, though it's not a runnable repro, so I can't be sure it isn't missing something (you haven't even shared the version of the provider you're using). See also #3707 for AI analysis.

[bdovaz]

It was because I had an EnsureCreated in the DbContext constructor, and that requires a connection string to be configured.

My mistake, sorry.