dotnet/efcore · error · OperationException

No DbContext was found in assembly

Error message

No DbContext was found in assembly '{assembly}'. Ensure that you're using the correct assembly and that the type is neither abstract nor generic.

What it means

OperationException thrown by DbContextOperations.DropDatabase when contextType == "*" (drop for every context in the assembly) but CreateAllContexts yielded no DbContext types. The wildcard loop ran zero times, so anyContext stays false.

Solutions

Run the command from the project/assembly that actually contains the concrete DbContext type.
Specify the explicit context name instead of '*' (e.g. --context MyContext).
Add [assembly: DbContext(typeof(MyContext))] in the startup assembly so discovery finds it.
Ensure the context class is non-abstract and non-generic.

Example fix

// before
> dotnet ef database drop --context * --project src/MyApp.Domain

// after
> dotnet ef database drop --context MyApp.Data.AppDbContext --project src/MyApp.Api

Defensive patterns

Strategy: validation

Validate before calling

var contexts = operations.GetContextTypes().ToList();
if (contextType == "*" && contexts.Count == 0)
{
    throw new InvalidOperationException(
        $"No DbContext in assembly '{assemblyName}'; cannot drop for all contexts.");
}

Try / catch

try { operations.DropDatabase("*", null); }
catch (OperationException ex) when (ex.Message.Contains("No DbContext was found"))
{ /* point tooling at the correct assembly */ }

Prevention

Run EF tools from the startup project that owns the contexts.
Prefer naming --context explicitly over relying on '*'.
Add [assembly: DbContext(typeof(...))] to make discovery robust.

When it happens

Trigger: Running `dotnet ef database drop --context *` (or programmatic DropDatabase with contextType "*") in a startup/project assembly that contains no concrete, non-generic, non-abstract DbContext-derived types.

Common situations: Pointing the tools at the wrong assembly (a class library instead of the startup project), all contexts live behind a test/abstraction layer the discovery cannot instantiate, or DbContext types are abstract base classes only.

Related errors

AI-assisted analysis of dotnet/efcore@3a2006ef56 (2026-08-11). Data as JSON: /api/errors/cb48cc9d264cc28f. Report an issue: GitHub.

Appendix: source

Thrown at src/EFCore.Design/Design/Internal/DbContextOperations.cs:120

    /// </summary>
    public virtual void DropDatabase(string? contextType, string? connectionString)
    {
        if (contextType == "*")
        {
            var anyContext = false;

            foreach (var contextItem in CreateAllContexts())
            {
                anyContext = true;
                using (contextItem)
                {
                    DropDatabaseContext(contextItem, connectionString);
                }
            }

            if (!anyContext)
            {
                throw new OperationException(DesignStrings.NoContext(_assembly.GetName().Name));
            }

            return;
        }

        using var context = CreateContext(contextType);
        DropDatabaseContext(context, connectionString);
    }

    private void DropDatabaseContext(DbContext context, string? connectionString)
    {
        if (connectionString is not null)
        {
            context.Database.SetConnectionString(connectionString);
        }

        var connection = context.Database.GetDbConnection();
        _reporter.WriteInformation(DesignStrings.DroppingDatabase(connection.Database, connection.DataSource));

View on GitHub (pinned to 3a2006ef56)