microsoft/aspire · error · InvalidOperationException

A database name is required but was not provided. Specify…

Error message

A database name is required but was not provided. Specify it via the '{nameof(databaseName)}' parameter, the '{nameof(MongoDBEntityFrameworkCoreSettings.DatabaseName)}' setting, or include it in the connection string.

What it means

MongoDB requires a database name for UseMongoDB(connectionString, databaseName). The AddMongoDbContext ConfigureDbContext callback validates the connection string first, then throws if settings.DatabaseName is still null/empty — meaning the databaseName parameter, the MongoDBEntityFrameworkCoreSettings.DatabaseName setting, and the 'Database=' part of the connection string were all absent.

Solutions

Use the AddMongoDbContext overload that takes a databaseName parameter.
Or append the database to the connection string: mongodb+srv://.../mydb.
Or set DatabaseName in the 'Aspire:MongoDB:EntityFrameworkCore' configuration section (or the :<TContext.Name> override).
Ensure the EF design-time factory also supplies a database name when running 'dotnet ef' commands.

Example fix

// before
builder.AddMongoDbContext<CatalogContext>("mongo"); // connection string has no /db
// after
builder.AddMongoDbContext<CatalogContext>("mongo", "catalog");
// or: "ConnectionStrings": { "mongo": "mongodb+srv://user:pass@cluster/catalog" }

Defensive patterns

Strategy: validation

Validate before calling

// before AddMongoDbContext without a databaseName parameter
var cs = builder.Configuration.GetConnectionString(connectionName) ?? "";
var dbNameFromCs = cs.Split('/').LastOrDefault(p => p.Contains('?') ? p.Split('?')[0].Length > 0 : p.Length > 0);
var settingDb = builder.Configuration["Aspire:MongoDB:EntityFrameworkCore:DatabaseName"];
if (string.IsNullOrEmpty(dbNameFromCs) && string.IsNullOrEmpty(settingDb))
{
    throw new InvalidOperationException("MongoDB database name must come from the parameter, settings, or connection string.");
}

Type guard

bool HasMongoDatabaseName(string? param, string? settingDb, string? cs) => !string.IsNullOrEmpty(param) || !string.IsNullOrEmpty(settingDb) || (cs?.Split('/').LastOrDefault()?.Split('?')[0].Length > 0);

Try / catch

try { builder.AddMongoDbContext<CatalogContext>("mongo"); }
catch (InvalidOperationException ex) when (ex.Message.Contains("A database name is required")) { builder.AddMongoDbContext<CatalogContext>("mongo", "catalog"); }

Prevention

Pass the databaseName parameter explicitly instead of relying on connection-string inference.
When copying Atlas connection strings, remember to append /databasename before any '?'.
If you use EF design-time factories, give them a database name too or 'dotnet ef' will fail.

When it happens

Trigger: Calling AddMongoDbContext<TContext>(connectionName) without a databaseName argument where the connection string has no database part and the settings section lacks DatabaseName; validation happens lazily when the DbContext options are configured.

Common situations: Connection string copied from Atlas (e.g. mongodb+srv://user:pass@cluster/) without /dbname; refactor from the named overload to the inferred overload; DatabaseName key typo'd in the 'Aspire:MongoDB:EntityFrameworkCore' section; EF design-time factory generating options with a bare connection string.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/b417330ac07209c4. Report an issue: GitHub.

Appendix: source

Thrown at src/Components/Aspire.MongoDB.EntityFrameworkCore/AspireMongoDBEntityFrameworkCoreExtensions.cs:86

            if (!string.IsNullOrEmpty(mongoUrl.DatabaseName))
            {
                settings.DatabaseName = mongoUrl.DatabaseName;
            }
        }

        configureSettings?.Invoke(settings);

        builder.Services.AddDbContextPool<TContext>(ConfigureDbContext);

        ConfigureInstrumentation<TContext>(builder, settings);

        void ConfigureDbContext(DbContextOptionsBuilder dbContextOptionsBuilder)
        {
            ConnectionStringValidation.ValidateConnectionString(settings.ConnectionString, connectionName, DefaultConfigSectionName, $"{DefaultConfigSectionName}:{typeof(TContext).Name}", isEfDesignTime: EF.IsDesignTime);

            if (string.IsNullOrEmpty(settings.DatabaseName))
            {
                throw new InvalidOperationException($"A database name is required but was not provided. Specify it via the '{nameof(databaseName)}' parameter, the '{nameof(MongoDBEntityFrameworkCoreSettings.DatabaseName)}' setting, or include it in the connection string.");
            }

            dbContextOptionsBuilder.UseMongoDB(settings.ConnectionString!, settings.DatabaseName);

            configureDbContextOptions?.Invoke(dbContextOptionsBuilder);
        }
    }

    /// <summary>
    /// Configures logging and telemetry for the <see cref="DbContext" />.
    /// </summary>
    /// <typeparam name="TContext">The <see cref="DbContext" /> that needs to be configured.</typeparam>
    /// <param name="builder">The <see cref="IHostApplicationBuilder" /> to read config from and add services to.</param>
    /// <param name="configureSettings">An optional delegate that can be used for customizing options. It's invoked after the settings are read from the configuration.</param>
    /// <remarks>Reads the configuration from "Aspire:MongoDB:EntityFrameworkCore:{typeof(TContext).Name}" config section, or "Aspire:MongoDB:EntityFrameworkCore" if former does not exist.</remarks>
    /// <exception cref="ArgumentNullException">Thrown if mandatory <paramref name="builder"/> is null.</exception>
    /// <exception cref="InvalidOperationException">Thrown when mandatory <see cref="DbContext"/> is not registered in DI.</exception>
    public static void EnrichMongoDbContext<[DynamicallyAccessedMembers(RequiredByEF)] TContext>(

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