Exclude property of model in insert Entity Framework

I get an error when inserting data into my database. My database columns are:

username, password 

and I added confirmpassword to the model to extend it.

How do I get rid of the confirmpassword to insert the username and password while using the model with confirmpassword property?

My code:

BootstrapTrainingEntities db = new BootstrapTrainingEntities();

var u = new User();

u.username = user.username;
u.password = user.password;
// how to I remove or ignore the confirmPassword property when saving?

db.Users.Add(u);
db.SaveChanges();

Model

[MetadataType(typeof(metadataUser))]
public partial class User
{
    public string confirmPassword { get; set; }
}

public class metadataUser
{
    [Required(ErrorMessage = "Username is required", AllowEmptyStrings = false)]
    [Display(Name ="Username")]
    public string username { get; set; }

    [Required(ErrorMessage ="Password is required", AllowEmptyStrings = false)]
    [Display(Name = "Password")]
    [DataType(DataType.Password)]
    public string password { get; set; }

    [Required(ErrorMessage ="Confirmation Password is required", AllowEmptyStrings = false)]
    [Display(Name ="Confiramation Password")]
    [DataType(DataType.Password)]
    [Compare("password",ErrorMessage = "Password does not match")]
    public string confirmPassword { get; set; }
}