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

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.

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,

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)

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)`.

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();
}
}

**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][1] 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()**;





[1]:

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