EF Code First "Invalid column name 'Discriminator'" but no inheritance

Here is the Fluent API syntax.

http://blogs.msdn.com/b/adonet/archive/2010/12/06/ef-feature-ctp5-fluent-api-samples.aspx

class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string FullName { 
        get {
            return this.FirstName + " " + this.LastName;
        }
    }
}

class PersonViewModel : Person
{
    public bool UpdateProfile { get; set; }
}


protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    // ignore a type that is not mapped to a database table
    modelBuilder.Ignore<PersonViewModel>();

    // ignore a property that is not mapped to a database column
    modelBuilder.Entity<Person>()
        .Ignore(p => p.FullName);

}

Turns out that Entity Framework will assume that any class that inherits from a POCO class that is mapped to a table on the database requires a Discriminator column, even if the derived class will not be saved to the DB.

The solution is quite simple and you just need to add [NotMapped] as an attribute of the derived class.

Example:

class Person
{
    public string Name { get; set; }
}

[NotMapped]
class PersonViewModel : Person
{
    public bool UpdateProfile { get; set; }
}

Now, even if you map the Person class to the Person table on the database, a "Discriminator" column will not be created because the derived class has [NotMapped].

As an additional tip, you can use [NotMapped] to properties you don't want to map to a field on the DB.