User secrets getting loaded at runtime but not at design time

I’m using IHost to create a service provider in a console app. I have set up user secrets that get loaded when running the project. However when I use the Package Manager Console with commands like Add-Migration user secrets don’t get loaded.

public static async Task Main()
{
    IHost host = Host.CreateDefaultBuilder()
        .ConfigureServices((context, serviceCollection) =>
        {
            serviceCollection
                .AddDbContext<ApplicationDbContext>();
        })
        .Build();

    // Other code
}

public class ApplicationDbContext(IConfiguration configuration) : DbContext
{
    public DbSet<TestRequest> TestRequests { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        // This foreach loop doesn't log anything stored in user secrets at design-time while it does at runtime
        foreach (var item in configuration.AsEnumerable())
        {
            Console.WriteLine(item);
        }

        string connStr = configuration.GetConnectionString("MySql") ??
            throw new NullReferenceException("MySQL conncetion string was null"); // Throws at design time

        optionsBuilder
            .UseMySql(connStr, ServerVersion.AutoDetect(connStr));
    }
}

My user secrets ID is set in the .csproj file.

secrets.json

{
    "ConnectionStrings:MySql": "Server=localhost;Database=db;Uid=root;Pwd=mypwd;"
}

>Solution :

This issue occurs because configuration data (especially user secrets) isn’t loaded at design-time. When you run your application, Host.CreateDefaultBuilder() loads the configuration and user secrets, but when running commands like Add-Migration, this doesn’t happen.

To fix this, you can create a class that implements the IDesignTimeDbContextFactory<T> interface. This class tells Entity Framework how to create your DbContext at design time.

Here’s how you can do it:

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Design;
using Microsoft.Extensions.Configuration;

public class ApplicationDbContextFactory : IDesignTimeDbContextFactory<ApplicationDbContext>
{
    public ApplicationDbContext CreateDbContext(string[] args)
    {
        IConfigurationRoot configuration = new ConfigurationBuilder()
            .AddJsonFile("appsettings.json") // If needed
            .AddUserSecrets<ApplicationDbContextFactory>()
            .Build();

        var optionsBuilder = new DbContextOptionsBuilder<ApplicationDbContext>();

        string connStr = configuration.GetConnectionString("MySql") ??
            throw new NullReferenceException("MySQL connection string was null");

        optionsBuilder.UseMySql(connStr, ServerVersion.AutoDetect(connStr));

        return new ApplicationDbContext(configuration, optionsBuilder.Options);
    }
}

Then, update your ApplicationDbContext class like this:

public class ApplicationDbContext : DbContext
{
    private readonly IConfiguration _configuration;

    public ApplicationDbContext(IConfiguration configuration, DbContextOptions<ApplicationDbContext> options)
        : base(options)
    {
        _configuration = configuration;
    }

    public DbSet<TestRequest> TestRequests { get; set; }

    // You can remove the OnConfiguring method if you don't need it anymore
}

By doing this, the configuration and user secrets will be loaded at design-time as well, so the Add-Migration command will find the connection string.