Question

I have a concern like this: in the database, there will be no distinct tables for passengers, drivers or managers, but only a users table. therefore there should only be User entity (EF Core) to map to the table. however, the users table has one-to-many relationship with vehicles, and this should only apply to users that have role driver (Role is an entity, representing the roles table). How should I handle this?

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Answer

This is a common issue in EF Core when using a single "Users" table for multiple roles while enforcing role-based constraints . Since only drivers should have a vehicles relationship, you have a few design options:

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Option 1: Use Navigation Property with Conditional Loading

You keep a single User entity , but filter vehicle access based on role .

Implementation

public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    public Role Role { get; set; }  // Navigation property to Role
    public int RoleId { get; set; } // Foreign Key

    // Navigation property: Only relevant for Drivers
    public List<Vehicle>? Vehicles { get; set; }
}

public class Vehicle
{
    public int Id { get; set; }
    public string LicensePlate { get; set; }
    public int UserId { get; set; } // FK to User
    public User User { get; set; }  // Navigation property
}

Enforcing the Role Restriction

You filter access to vehicles in queries (prevent non-drivers from having vehicles):

var driversWithVehicles = dbContext.Users
    .Where(u => u.Role.Name == "Driver")
    .Include(u => u.Vehicles)
    .ToList();

📌 Pros : Keeps database simple, avoids unnecessary table inheritance.

📌 Cons : Need to manually enforce role-based constraints in logic.

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Option 2: Use Backing Fields with Explicit Role Checks

Instead of exposing Vehicles to all users, use a private backing field to ensure only drivers have access.

Implementation

public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    public Role Role { get; set; }
    public int RoleId { get; set; }

    // Private field (EF Core still maps this correctly)
    private List<Vehicle>? _vehicles;

    // Public property ensures only Drivers can access
    public IReadOnlyList<Vehicle>? Vehicles
        => Role?.Name == "Driver" ? _vehicles : null;
}

📌 Pros : Prevents incorrect usage at the code level.

📌 Cons : Requires manual enforcement at object level (EF Core does not enforce this automatically).

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Option 3: Table Splitting (Single Table with Different Mappings)

EF Core table splitting allows mapping a subset of properties only when a condition is met .

Implementation

public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    public Role Role { get; set; }
}

public class Driver
{
    public int Id { get; set; } // Same as User Id
    public List<Vehicle> Vehicles { get; set; }
}

EF Core Fluent API Mapping

modelBuilder.Entity<User>()
    .ToTable("Users");

modelBuilder.Entity<Driver>()
    .ToTable("Users") // Same table
    .HasOne<Role>()
    .WithMany()
    .HasForeignKey(u => u.Id)
    .HasPrincipalKey(u => u.Id);

📌 Pros : EF Core ensures only drivers have vehicles automatically.

📌 Cons : More complex EF Core configuration.

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Which Approach is Best?

Approach	Simplicity	Enforces Role Constraint	Works Well with EF Core
1: Conditional Loading	✅ Simple	❌ Manual enforcement	✅ Good for performance
2: Backing Fields	✅ Simple	✅ Enforces constraint	✅ Works well
3: Table Splitting	❌ Complex	✅ Automatic enforcement	✅ EF Core manages well

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📌 Recommendation

• If you want a simple solution → Use Option 1 (Conditional Loading)
• If you want stricter role constraints → Use Option 2 (Backing Fields)
• If EF Core should enforce the structure automatically → Use Option 3 (Table Splitting)

Do you want help implementing one of these fully in Fluent API ? 🚀

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References

• Navigation property