propertyName' cannot be used as a property on entity type 'typeName' because it is configured as a navigation

Question

I have an entity user with the following:

public class User
{
    [Key, Required]
    public int Id { get; set; }
    public int GenderId { get; set; }
    public virtual Gender Gender { get; set; }
}

In gender:

public class Gender
{
    [Key, Required]
    public int Id { get; set; }
    public virtual ICollection<User> Users { get; set; }
}

Then, inside my DbContext, I have:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<User>(user =>
    {
        user
        .HasOne(x => x.Gender)
        .WithMany(x => x.Users)
        .HasForeignKey(x => x.GenderId);
    }

    user.HasIndex(x => x.Gender);
}

When I run dotnet ef add migration User, I am getting the error:

'Gender' cannot be used as a property on entity type 'User' because it is configured as a navigation.

Answer 1

I was trying to create an index on a navigation property. Instead, create the index on the foreign key.

Change user.HasIndex(x => x.Gender) to user.HasIndex(x => x.GenderId).

Answer 2

Use [ForeignKey("GenderId")] on your public virtual Gender Gender { get; set; } property . Thus GenderId would be identified as a foreign key for Associated User.

See below updated code:

public class User
{
    public int GenderId { get; set; }
    [ForeignKey("Id")]//Gender Primary key
    public virtual Gender Gender { get; set; }
}

Hope it will fix your issue.

Thanks,

Answer 3

I had a similar error:

'Product' cannot be used as a property on entity type 'OrderLine' because it is configured as a navigation.

The cause of the error was that in the fluent api I also used the entity as a property:

modelBuilder.Entity<OrderLine>().Property(ol => ol.Product).IsRequired(true)

Answer 4

I had the same problem for a complex hierarchy model with nested complex classes in it.
Apparently, the IsRequired() method conflicts with OnDelete(...). I removed the IsRequired() and everything got back to normal.

public class MyComplexClassConfig : IEntityTypeConfiguration<MyComplexClass>
{
    public void Configure(EntityTypeBuilder<MyComplexClass> builder)
    {
        builder
            .HasOne(col => col.ChildClass)
            .WithOne(col => col.ParentClass)
            .OnDelete(DeleteBehavior.Cascade);
            
        // The following line of code needs to be deleted.
        builder.Property(col => col.Customer).IsRequired();
    }
}

Answer 5

An update due to a similar problem:

I had same problem when I was stablishing a relation between Product Entity and Warranti Entity as below:

public class Product
{
    public long Id { get; set; }
    public string Images { get; set; }
    public string Brand { get; set; }
    public Warranti Warranti { get; set; }
}


public class Warranti
{
    public Product Product { get; set; }
    public long ProductId { get; set; }
    public int WarrantyPeriod { get; set; }
}

and on my DatabaseContext Class I had this config:

  protected override void OnModelCreating(ModelBuilder modelBuilder)  
   {
        modelBuilder.Entity<Product>()
            .HasOne(p => p.Warranti)
            .WithOne(p => p.Product)
            .HasForeignKey<Warranti>(p => p.Product);
    }

And I got Same error. But, What was The problem?

According to Microsoft Official EFCore Doc The ForeignKey Should be something like this:

.HasForeignKey(p => p.BlogForeignKey); // single prop such as string or int,...

Or

 .HasForeignKey("BlogForeignKey"); // Hardcoded favorite string

But I was Using a class(Product) instead of a property In HasForeignKey method. likewise, you were using a class(Gender) instead of a property In HasIndex method. Changing these classes to an Id property solves the problem.

As a conclusion: Try to use an Id property on HasForeignKey() and HasIndex();