Как добавить SelectedValue из Combobox в Запрос

Пробую добавить данные в БД из формы, выдается ошибка, что "Строка имела не верный формат". Добавление:

        private RelayCommand addCmd;
        public RelayCommand AddCmd
        {
            get
            {
                return addCmd ?? (
                addCmd = new RelayCommand(obj =>
                {
                    using (dbEntities db = new dbEntities())
                    {
                        users users = new users
                        {
                            secondname = Secondname.Trim(),
                            firstname = Firstname.Trim(),
                            middlename = Middlename.Trim(),
                            datebirth = BirthDate,
                            gender = Genders.Select(a => a.Value).ToString(),
                            iddivision = int.Parse(Division.Select(d=> d.iddivision).ToString())
                        };

                        db.users.Add(users);
                        db.SaveChanges();
                    }

                }));
            }
        }

XAML:

 <TextBox x:Name="txtSecondName" Text="{Binding Secondname}" />
        <TextBox x:Name="txtFirstName" Text="{Binding Firstname}" />
        <TextBox x:Name="txtMidName" Text="{Binding Middlename}" />
        <ComboBox x:Name="cbGender" 
                          ItemsSource="{Binding Genders}" 
                          SelectedValuePath="Value" 
                          DisplayMemberPath="Name" 
                          IsSynchronizedWithCurrentItem="True" />
        <DatePicker x:Name="dpBirth" SelectedDate="{Binding BirthDate}" />
        <ComboBox x:Name="cbDivision" 
                          ItemsSource="{Binding Division}" 
                          SelectedValuePath="iddivision" 
                          DisplayMemberPath="namedivision" 
                          IsSynchronizedWithCurrentItem="True" />
        <Button x:Name="buttAdd" Command="{Binding AddCmd}" Content="Добавить" />

Заполнение ComboBox:

Division = new ObservableCollection<ModelDivision>(ModelDivision.GetDivision());
Genders = new ObservableCollection<ModelGender>(ModelGender.GetGenders());

В котором

public partial class ModelGender
    {
        public string Value { get; set; }
        public string Name { get; set; }

        public static List<ModelGender> GetGenders()
        {
            List<ModelGender> genders = new List<ModelGender>();
            genders.Add(new ModelGender() { Value = "1", Name = "М" });
            genders.Add(new ModelGender() { Value = "2", Name = "Ж" });
            return genders;
        }
    }

public partial class ModelDivision
{

//here - getters and setters

 public static List<ModelDivision> GetDivision()
       {

            using (dbEntities db = new dbEntities())
            {
                var query = db.division.ToList().Join(db.users,
                        u => u.iduser,
                        d => d.iduser,
                        (u, d) => new ModelDivision
                        {
                            iddivision = u.iddivision,
                            namedivision = u.namedivision,
                            secondnameuser = d.secondname,
                            firstnameuser = d.firstname,
                            middlenameuser = d.middlename
                        }).ToList();
                return query;
            }
        }
}
}