"Cannot insert explicit value for identity column in table" when inserting object with EF Core

I am trying to insert a new row to my table, using EF Core, SQL Server and C#, but I am having trouble getting EF Core to use the identity column properly.

Here's what I am doing:

I am creating a new object using the Entity Framework generated class (I've included the entity class definition at the end of my post)

EmployeePermissions employee_permission = new EmployeePermissions
{
    FkEmployee = PkEmployee,
    FkPermission = permission_key
};

Then I call db.EmployeePermissions.add(employee_permission), which works on all of my calls where an object comes from [FromBody] <Entity Class> <object_variable> (albeit using other tables).

But here, when I instantiate the class myself, I get this error:

SqlException (0x80131904): Cannot insert explicit value for identity column in table 'Employee_Permissions' when IDENTITY_INSERT is set to OFF.

I don't understand why this is happening — I want it to auto increment the identity column. I used ObjectDumper to see what is getting passed to .Add(), which is as follows:

properties {
    PkEmployeePermissions = 0 [System.Int32] // this is the identity column, of course
    FkEmployee = 31 [System.Int32]
    FkPermission = 6 [System.Int32]
    FkEmployeeNavigation = <null>
    FkPermissionNavigation = <null>
}

I have investigated the other calls which are working fine (the ones where [FromBody] creates an object) and the identity column simply equals 0 in those calls too, so I don't understand what is different here.

Have I misconfigured something in the database? I have double checked in the column properties that the column PkEmployeePermissions is indeed an identity column, so it should be auto incremented.

Here's the Entity class if it helps:

public partial class EmployeePermissions
{
    public int PkEmployeePermissions { get; set; }
    public int FkEmployee { get; set; }
    public int FkPermission { get; set; }

    public Employee FkEmployeeNavigation { get; set; }
    public Permission FkPermissionNavigation { get; set; }
}

The default convention is for the primary key of a class to be called either Id or (classname)Id - this is not the case in your class.

Also: if you're mapping to an IDENTITY column in SQL Server, you must add a relevant data annotation to the key column.

Try this:

public partial class EmployeePermissions
{
    // add the [Key] annotation to indicate the primary key of the class/table
    [Key]
    // add the [DatabaseGenerated(..)] annotation to indicate an IDENTITY column in the table
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int PkEmployeePermissions { get; set; }
    public int FkEmployee { get; set; }
    public int FkPermission { get; set; }

    public Employee FkEmployeeNavigation { get; set; }
    public Permission FkPermissionNavigation { get; set; }
}

Now you should be able to insert those objects, and have them stored properly in your SQL Server table.