Automapping an object with a child collection NHibernate - asp.net-mvc

Question

I just recently switched from EF5 to NHibernate due to a few features that I want in my ORM but didn't find in EF. So, I'm new to NHibernate. I'm working in ASP.Net MVC.
I'm using Automapper to map FNH objects to my view models, but I'm having issues translating previously how I did things in EF to FNH. For example, I have a self referencing table that is a menu system.
Here is the model:
public partial class Menu {
private int _Id;
private string _Title;
private string _Link;
private int _SortOrder;
private System.Nullable<int> _ParentMenuId;
private Iesi.Collections.ISet _ChildMenus;
private Menu _ParentMenu;
#region Extensibility Method Definitions
partial void OnCreated();
#endregion
public Menu()
{
this._ChildMenus = new Iesi.Collections.HashedSet();
OnCreated();
}
/// <summary>
/// There are no comments for Id in the schema.
/// </summary>
public virtual int Id
{
get
{
return this._Id;
}
set
{
this._Id = value;
}
}
/// <summary>
/// There are no comments for Title in the schema.
/// </summary>
public virtual string Title
{
get
{
return this._Title;
}
set
{
this._Title = value;
}
}
/// <summary>
/// There are no comments for Link in the schema.
/// </summary>
public virtual string Link
{
get
{
return this._Link;
}
set
{
this._Link = value;
}
}
/// <summary>
/// There are no comments for SortOrder in the schema.
/// </summary>
public virtual int SortOrder
{
get
{
return this._SortOrder;
}
set
{
this._SortOrder = value;
}
}
/// <summary>
/// There are no comments for ParentMenuId in the schema.
/// </summary>
public virtual System.Nullable<int> ParentMenuId
{
get
{
return this._ParentMenuId;
}
set
{
this._ParentMenuId = value;
}
}
/// <summary>
/// There are no comments for ChildMenus in the schema.
/// </summary>
public virtual Iesi.Collections.ISet ChildMenus
{
get
{
return this._ChildMenus;
}
set
{
this._ChildMenus = value;
}
}
/// <summary>
/// There are no comments for ParentMenu in the schema.
/// </summary>
public virtual Menu ParentMenu
{
get
{
return this._ParentMenu;
}
set
{
this._ParentMenu = value;
}
}
}
Here is the Mapping:
public class MenuMap : ClassMap<Menu>
{
public MenuMap()
{
Schema(#"dbo");
Table(#"Menus");
LazyLoad();
Id(x => x.Id)
.Column("Id")
.CustomType("Int32")
.Access.Property()
.CustomSqlType("int")
.Not.Nullable()
.Precision(10)
.GeneratedBy.Identity();
Map(x => x.Title)
.Column("Title")
.CustomType("String")
.Access.Property()
.Generated.Never()
.CustomSqlType("varchar");
Map(x => x.Link)
.Column("Link")
.CustomType("String")
.Access.Property()
.Generated.Never()
.CustomSqlType("varchar")
.Not.Nullable()
.Length(50);
Map(x => x.SortOrder)
.Column("SortOrder")
.CustomType("Int32")
.Access.Property()
.Generated.Never()
.Not.Nullable()
.UniqueKey("KEY1");
Map(x => x.ParentMenuId)
.Column("ParentMenuId")
.CustomType("Int32")
.Access.Property()
.Generated.Never()
.UniqueKey("KEY1");
HasMany<Menu>(x => x.ChildMenus)
.Access.Property()
.AsSet()
.Cascade.None()
.LazyLoad()
.Inverse()
.Not.Generic()
.KeyColumns.Add("ParentMenuId", mapping => mapping.Name("ParentMenuId")
.SqlType("int")
.Nullable());
References(x => x.ParentMenu)
.Class<Menu>()
.Access.Property()
.Cascade.None()
.LazyLoad()
.Columns("ParentMenuId");
}
}
Here is my View Model or DTO:
public class MainMenuItemViewModel
{
public Int32 Id { get; set; }
public string Title { get; set; }
public string Link { get; set; }
public Int32 SortOrder { get; set; }
public Int32? ParentMenuId { get; set; }
public IList<MainMenuItemViewModel> ChildMenus { get; set; }
}
When I try to map the domain object to the view model, using this:
Mapper.CreateMap<Menu, MainMenuItemViewModel>();
I get the following error on I check if the configuration is valid on run:
The following property on WinStream.WebUI.Models.MainMenuItemViewModel cannot be mapped: ChildMenus
Add a custom mapping expression, ignore, add a custom resolver, or modify the destination type WinStream.WebUI.Models.MainMenuItemViewModel.
Context:
Mapping to property ChildMenus from System.Object to WinStream.WebUI.Models.MainMenuItemViewModel
Mapping to property ChildMenus from Iesi.Collections.ISet to System.Collections.Generic.IList`1[[WinStream.WebUI.Models.MainMenuItemViewModel, WinStream.WebUI, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]
Mapping from type WinStream.Services.Entities.Menu to WinStream.WebUI.Models.MainMenuItemViewModel
Exception of type 'AutoMapper.AutoMapperConfigurationException' was thrown.
I thought it might be related to converting ISet to IList, so I put in an ISet in my view model, but still had the issue.
Thank you for your help - I realize this could be a complete newbie question, but I couldn't find much help through Google. I've been struggling with this for several days now.
Thanks!
EDIT:
I have gotten past the error above, but now when I'm querying the database, the ChildMenus collection for the root object includes a null object for every child object in the database, including the associated child objects, instead of just the actual related child objects.
For example:
Root Menu
ChildMenus collection is supposed to have 3 child objects, but it has 8 (5 null and 3 populated)
List item
ChildMenus collection is supposed to have 1 child objects, but it has 8 (7 null and 1 populated)
List item
ChildMenus collection is supposed to have 0 child objects, and it has no child objects.
This is the code:
IList<Menu> menus = session.Query<Menu>().Where(x => x.ParentMenuId== null).ToList()
Any ideas on this, or do I need to put it into another question? Thank you!

Answer 1

NHibernate doesn't need a lot of the workarounds from EF. You basicly have a menu with ordered childmenues having a parent reference.
public class Menu
{
public int Id { get; protected set; }
public string Title { get; set; }
public string Link { get; set; }
public IList<Menu> ChildMenus { get; protected set; }
public Menu ParentMenu { get; set; }
public Menu()
{
ChildMenus = new List<Menu>();
}
}
public class MenuMap : ClassMap<Menu>
{
public MenuMap()
{
Table(#"Menus");
Id(x => x.Id).GeneratedBy.Identity();
Map(x => x.Title).Length(100);
Map(x => x.Link).Length(50);
HasMany<Menu>(x => x.ChildMenus)
.AsList("SortOrder")
.Inverse()
.KeyColumn("ParentMenuId");
References(x => x.ParentMenu).Column("ParentMenuId");
}
}
Notes:
Schema should be defined by convention or as default schema/catalog in the Configuration object
remove all unnessesary declarations from the mapping because it often introduces portability issues (eg. customsqltypes), complicates the code and prevents conventions
customsqltype() renders length() useless
Sortorder is not really needed because the list already defines the order
parentId is duplicate for Parent.Id and can be implemented if needed ParentId { get { return ParentMenu == null ? null : (int?)ParentMenu.Id } }, no need to map or store it in field
if the parentreference is not needed remove it and .Inverse() from the collection mapping