实体框架SaveChanges不保存到数据库

当我在它周围放置一个try catch时，我的代码没有出错或任何东西，但它仍然没有保存到数据库。我是不是漏掉了什么?

var newGroupMemberOf = new GroupMemberOf();
newGroupMemberOf.SamAcName = accountName;
newGroupMemberOf.MemberOf = parentSameAcName;
newGroupMemberOf.DateCreated = DateTime.Now;
newGroupMemberOf.DateUpdated = DateTime.Now;
newGroupMemberOf.IsActive = true;
newGroupMemberOf.Hidden = hidden;
newGroupMemberOf.ID = 12345678;
UserEntities.GroupMemberOf.Add(newGroupMemberOf);
UserEntities.SaveChanges();

我的实体集看起来有点像

public partial class UsersEntities : DbContext 
{ 
 public UsersEntities() 
    : base("name=UsersEntities") 
{ 
} 
protected override void OnModelCreating(DbModelBuilder modelBuilder) 
 {
  throw new UnintentionalCodeFirstException(); 
 }
 public virtual DbSet<GroupMemberOf> GroupMemberOf { get; set; }