Unidirectional Many to Many Relationship With Entity Framework Code First on Windows Azure SQL Database

There are times when entities don’t need navigation properties on both sides of the relationship. This is an example you can use to map to an existing database or generate a brand new database on Windows Azure SQL Database.

The ERD shows a Many to Many relationship between the FlightLog and the Airport entities. The requirements for the current model has no need for Airport to have a Navigation Property of FlightLogs.

Using Entity Frame Work Code First, the following statement can be used in the EntityTypeConfiguration to configure the relationship.

HasMany(r => r.Airports)
    .WithMany() // No navigation property here
    .Map(m =>
        {
            m.MapLeftKey("FlightLogId");
            m.MapRightKey("AirportId");
            m.ToTable("BridgeTableForAirportsAndFlightlogs");
        });

FlightLog has many Airports, the relationship is held in an intermediate table called BridgeTableForAirportsAndFlightlogs. By not specifying a property for the inverse Navigation Property, a unidirectional Many to Many relationship is created.