关于多对多关系表无法更新与插入的问题

public partial class WebManageRoles : Lind.DDD.Domain.Entity
{
public WebManageRoles()
{
this.WebManageMenus = new List<WebManageMenus>();
this.WebManageUsers = new List<WebManageUsers>();
}
[DisplayName("名称"), Required]
public string RoleName { get; set; }
[DisplayName("关于")]
public string About { get; set; }
[DisplayName("排序"), Required]
public int SortNumber { get; set; }
[DisplayName("最后操作人")]
public string Operator { get; set; }
[DisplayName("权限"), Required]
public int OperatorAuthority { get; set; }
[DisplayName("部门"), Required]
public int DepartmentID { get; set; }
public virtual WebDepartments WebDepartments { get; set; }
public virtual ICollection<WebManageMenus> WebManageMenus { get; set; }
public virtual ICollection<WebManageUsers> WebManageUsers { get; set; }
}

old.WebManageMenus = menuRepository.GetModel(i => menu.Contains(i.Id)).ToList();
old.DepartmentID = dept;
old.RoleName = entity.RoleName;
old.SortNumber = entity.SortNumber;
old.About = entity.About;
old.DataUpdateDateTime = DateTime.Now;
roleRepository.Update(old);

public ManagerContext()
: base("DefaultConnection")
{
this.Configuration.AutoDetectChangesEnabled = true;//对多对多，一对多进行curd操作时需要为true
this.Configuration.LazyLoadingEnabled = false;
this.Configuration.ProxyCreationEnabled = false;//禁止动态拦截System.Data.Entity.DynamicProxies.
}