dotnet/efcore · error · OperationException

The provider '{provider}' is not a Relational provider and t

Error message

The provider '{provider}' is not a Relational provider and therefore cannot be used with Migrations.

What it means

EnsureServices failed to resolve an IMigrator from the design-time service provider, meaning the active database provider is not a Relational provider. Migrations are a relational concept (they produce SQL); in-memory and other non-relational providers do not register a migrator. The thrown message names the provider (or 'Unknown' if IDatabaseProvider itself was absent).

Source

Thrown at src/EFCore.Design/Design/Internal/MigrationsOperations.cs:469

        if (string.Equals(name, contextClassName, StringComparison.Ordinal))
        {
            throw new OperationException(
                DesignStrings.ConflictingContextAndMigrationName(name));
        }

        var services = _servicesBuilder.Build(context);
        EnsureServices(services);

        return services;
    }

    private static void EnsureServices(IServiceProvider services)
    {
        var migrator = services.GetService<IMigrator>();
        if (migrator == null)
        {
            var databaseProvider = services.GetService<IDatabaseProvider>();
            throw new OperationException(DesignStrings.NonRelationalProvider(databaseProvider?.Name ?? "Unknown"));
        }
    }

    private void EnsureMigrationsAssembly(IServiceProvider services)
    {
        var assemblyName = _assembly.GetName();
        var options = services.GetRequiredService<IDbContextOptions>();
        var contextType = services.GetRequiredService<ICurrentDbContext>().Context.GetType();
        var optionsExtension = RelationalOptionsExtension.Extract(options);
        if (optionsExtension.MigrationsAssemblyObject == null
            || optionsExtension.MigrationsAssemblyObject != _assembly)
        {
            var migrationsAssemblyName = optionsExtension.MigrationsAssembly
                ?? optionsExtension.MigrationsAssemblyObject?.GetName().Name
                ?? contextType.Assembly.GetName().Name;
            if (assemblyName.Name != migrationsAssemblyName
                && assemblyName.FullName != migrationsAssemblyName)
            {

View on GitHub (pinned to dbf9771522)

Solutions

Switch OnConfiguring to a relational provider (UseSqlServer/UseNpgsql/UseSqlite/etc.) for the environment where you run migrations.
If you need InMemory for tests, gate provider selection by configuration so design-time uses a relational provider.
For a custom provider, derive from the relational infrastructure and register IMigrator.

Example fix

// before
options.UseInMemoryDatabase("Test");
// after (design-time / production)
options.UseSqlServer(connectionString);
// (and keep InMemory only under an IntegrationTest config flag)

Defensive patterns

Strategy: validation

Validate before calling

var provider = context.Database.ProviderName;
if (!IsRelational(provider)) throw new InvalidOperationException($"Provider '{provider}' is not relational and cannot use migrations.");
static bool IsRelational(string name) => name is not null && !name.EndsWith("InMemory", StringComparison.Ordinal);

Prevention

Reserve InMemory for tests; gate it behind an env flag.
Configure a relational provider in the design-time environment.
Assert provider is relational before invoking migrations in code.

When it happens

Trigger: DbContext.OnConfiguring uses UseInMemoryDatabase (or a custom non-relational provider) and you run any migrations command. services.GetService<IMigrator>() at line 465 returns null, databaseProvider is e.g. 'Microsoft.EntityFrameworkCore.InMemory'.

Common situations: Dev/test setup uses the InMemory provider and someone runs 'dotnet ef migrations add'; a provider selection bug returns the InMemory provider in production config; custom provider that doesn't implement the relational stack.

Related errors

AI-assisted analysis of dotnet/efcore@dbf9771522 (2026-08-06). Data as JSON: /api/errors/d443fbbc0da0f367. Report an issue: GitHub.