关于在数据库中创建表的DbUpdateException

Question

public class Degree
{ 
    [Key]
    [Required(ErrorMessage = "שדה חובה")]
    public string degNum { get; set; }
    public string degName { get; set; }
    public string degTaype { get; set; } 
    public string degLavel { get; set; } 
    public string degInstitution { get; set; }
}

namespace Academy1.Dal
{
    **public class DegreeDal: DbContext**
    {
        public DbSet<Degree> Degrees { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Entity<Degree>().ToTable("tblDegree");
        }

    }
}

  **public class DegreeController : Controller**
    {   public ActionResult Enter()
        {
            return View("Enter", new Degree());
        }
        public ActionResult Submit(Degree degree)
        {
            DegreeDal dal = new DegreeDal();

            if (ModelState.IsValid)
            {
                dal.Degrees.Add(degree);
                *`***dal.SaveChanges();***`*\\Here I got the error message

                return View("Submit", degree);
            }
               return View("Enter", degree);
        }

嗨，我正在尝试在sql数据库中创建一个表。我收到了这条消息：

  

“类型的例外   发生'System.Data.Entity.Infrastructure.DbUpdateException'   EntityFramework.dll但未在用户代码中处理“   dal.savechanges。

请帮助。