剃刀页面模型返回null

Question

在OnPost动作中，我收到：

  

System.NullReferenceException：'对象引用未设置为   对象的实例。'

     

ContactManager.Pages.Auth.LoginModel.user.get返回null。

在User use = Login(user.Email, user.Password);

Login.cshtml.cs：

{
     public User user { get; set; }

    public string Msg;

    private DatabaseContext db;
    public LoginModel(DatabaseContext _db)
    {
        db = _db;
    }

    public void OnGet()
    {
        user = new User();
    }

    public IActionResult OnPost()
    {
        User use = Login(user.Email, user.Password);
        if (use == null)
        {
            Msg = "Invalid";
            return Page();
        }
        else
        {
           HttpContext.Session.SetString("email", use.Email);
           return RedirectToPage("L_Success");

        }
    }

    private User Login(string email, string password)
    {
        var user = db.Users.SingleOrDefault(u => u.Email.Equals(email));
        if (user != null)
        {
            if(BCrypt.Net.BCrypt.Verify(password, user.Password))
            {
                return user;
            }

        }

        return null;
    }
}

}

用户模型：

namespace ContactManager.Models
{
    [Table("User")] 

    public class User {


    [Key]
    public int Id { get; set; }

    public string Email { get; set; }

    public string Password { get; set; }

    public string Fullname { get; set; }


}

}

我的上下文类别：

namespace ContactManager.Models
{
    public class DatabaseContext : DbContext
    {


    public DatabaseContext(DbContextOptions<DatabaseContext> options) : base(options)
    {

    }

    public DbSet<User> Users { get; set; }

    }

}