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fluent nhibernate one to many collection, filtered by enum

I think I have a design issue here.
essentially I have a class called office
class Office
{
public virtual long Id { get; set; }
public virtual string Code { get; set; }
public virtual IList<Person> Managers { get; set; }
public virtual IList<Person> Developers { get; set; }
public virtual IList<Person> TeaMakers { get; set; }
}
and a class called Person
class Person
{
public virtual long Id { get; set; }
public virtual string Name {get; set;}
public virtual StaffType Type { get; set;}
public virtual Office Office { get; set; }
}
and an enum called StaffType
public enum StaffType
{
MANAGER,
DEVELOPER,
TEAMAKER
}
Mapping the Person table is easy:
public class PersonMap: ClassMap<Person>
{
public PersonMap()
{
Table("Person");
Id(x => x.Id);
Map(x => x.Name);
References(x => x.Office).ForeignKey("Id").Not.Nullable()
Map(x => x.Type).CustomType<StaffType>();
}
}
but i am stumped on the office map. how to i get the map to use the enum to filter the 3 lists?
if i do this:
public class OfficeMap: ClassMap<Office>
{
public static string TableName = "Office";
public static string MappingColumn = TableName + "Id";
public OfficeMap()
{
Table(TableName);
Id(x => x.Id);
Map(x = x.Code);
HasMany(x => x.Managers)
.Cascade.AllDeleteOrphan()
.Fetch.Select()
.Inverse().KeyColumn(MappingColumn);
HasMany(x => x.Developers)
.Cascade.AllDeleteOrphan()
.Fetch.Select()
.Inverse().KeyColumn(MappingColumn);
HasMany(x => x.TeaMakers)
.Cascade.AllDeleteOrphan()
.Fetch.Select()
.Inverse().KeyColumn(MappingColumn);
}
}
fluency won't have the foggiest idea how to split the 3 collections up by the StaffType enum
Thanks for the help
Extra note: the Person table's Type field allways gets mapped as an int.

NHibernate supports filtering as a part of the mapping. Please, read here more 6.2. Mapping a Collection.
The trick is to add more SQL into the mapping. In fact, some WHERE Condition, to be evaluated during the collection load. Small extract from the documentation:
<map // or <set or <bag ...
name="propertyName" (1)
table="table_name" (2)
...
where="arbitrary sql where condition" (9)
And the description of the WHERE:
where (optional) specify an arbitrary SQL WHERE condition to be used
when retrieving or removing the collection (useful if the collection
should contain only a subset of the available data)
In your case, the fluent syntax is similar: ...Where("MyColumn = 'myValue' ");
A draft for your solution:
...
HasMany(x => x.Managers)
.Cascade.AllDeleteOrphan()
.Fetch.Select()
.Inverse().KeyColumn(MappingColumn)
.Where("Type = 1") // the Column name in the Person table
; // and the value 1 as the enum of the Manager
...
// The same for the others

I would model this as a simple one-to-many (Office has many Person) and add an extension method to IEnumerable<Person> to filter by StaffType. If needed, you can encapsulate access to the Person collection through AddManager etc. methods that enforce business rules.

HasMany Mapping but getting one element or get some of

public class Category
{
public virtual int Id { set; get; }
public virtual string Name { set; get; }
public virtual int CategoryOrder { set; get; }
public virtual IEnumerable<News> LatestNews { set; get; }
}
public sealed class CategoryMap :ClassMap<Category>
{
public CategoryMap()
{
LazyLoad();
Id(x => x.Id);
Map(x => x.Name);
Map(x => x.CategoryOrder);
HasMany(x => x.LatestNews);
}
}
IRepository<Category> newsRepo = new NHibernateRepository<Category>();
using(var session = newsRepo.GetSessionFactory().OpenSession())
using(var transaction = session.BeginTransaction())
{
var result = session.Query<Category>().OrderBy(x => x.CategoryOrder);
transaction.Commit();
}
I have this category class Which I want to display a (only one) News per category. Is this correct mapping? or should i change it to Map
When i run this, it gets all the news per category. But i want the latest news per category (only one). I can get the latest news by querying News.DateUpdated.
How should i change the query to get one news per category?
or how do I get some of the News? ie: limit the number of news I can query?

I think you can have your cake and eat it too. You have a list of News items, so just leave that. But add in another property that gets just the News item you want.
public class Category
{
public virtual int Id { set; get; }
public virtual string Name { set; get; }
public virtual int CategoryOrder { set; get; }
public virtual IEnumerable<News> AllNews { set; get; }
public virtual News LatestNews
{
get
{
// probably needs some work
return this.AllNews.OrderByDescending(n => n.SomeDateField).Take(1);
}
}
}
public sealed class CategoryMap :ClassMap<Category>
{
public CategoryMap()
{
LazyLoad();
Id(x => x.Id);
Map(x => x.Name);
Map(x => x.CategoryOrder);
HasMany(x => x.AllNews);
}
}

you can use lazy mode extra to achieve this,
public News GetLatestNews(Category cat)
{
var session = SessionFactory.CurrentSession;
var news = session.CreateFilter(cat.LatestNews , "order by categoryorder").SetFirstResult((page - 1) * pageSize).SetFirstResult(0).SetMaxResults(1).List().FirstOrDefault();
return news;
}
however if you try to access the LatestNews collection directly, this won't be of any use as it will load all the news objects associated with Category from db which would lower the performance.

Fluent NHibernate - Detached table mapping

Is there a way I can setup mapping for a table that doesn't have a direct reference to another table? It actually gets it's reference from another table that I do have a direct reference from.
This is what I have so far, but I'm not sure how to map the "LookupValue" in my MetaData model. It would need to map to MetaData if the [mdd].DefinitionType equals the [mdl].LookupType and the [md].DataValue equals the [mdl].LookupKey.
public class MetaData {
public virtual long TableID { get; set; }
public virtual MetaDataDefinition Definition { get; set; }
public virtual int DefinitionID { get; set; }
public virtual String DataValue { get; set; }
public virtual MetaDataLookup LookupValue { get; set; }
public override bool Equals(object obj) { ... }
public over int GetHashCode() { ... }
}
public class MetaDataDefinition {
public virtual long ID { get; set; }
public virtual string DefinitionName { get; set; }
public virtual string DefinitionType { get; set; }
}
public class MetaDataLookup {
public virtual string Type { get; set; }
public virtual string LookupKey { get; set; }
public virtual string LookupValue { get; set; }
public override bool Equals(object obj) { ... }
public over int GetHashCode() { ... }
}
public class MetaDataMap : ClassMap<MetaData> {
public MetaDataMap() {
Table("PPOMetaData");
CompositeId()
.KeyProperty(x => x.TableID, "TableID")
.KeyProperty(x => x.DefinitionID, "DefinitionID");
References(x => x.Defintion, "DefinitionID").Not.LazyLoad().Cascade.All().Fetch.Join();
Map(x => x.TableID);
Map(x => x.DataValue);
}
}
public class MetaDataDefinitionMap : ClassMap<MetaDataDefinition> {
public MetaDataDefinitionMap() {
Table("MetaDataDefinitions");
Id(x => x.ID);
Map(x => x.DefinitionName);
Map(x => x.Type);
}
}
public class MetaDataLookupMap : ClassMap<MetaDataLookup> {
public MetaDataLookupMap() {
CompositeId()
.KeyProperty(x => x.LookupType)
.KeyProperty(x => x.LookupKey);
Map(x => x.LookupValue);
}
}
Ideally, I want to have it run a query similar to this:
SELECT data.TableID, data.DefinitionID, def.DefinitionName, data.DataValue,lu.LookupValue AS DataValue
FROM dbo.PPOMetadata AS data
INNER JOIN dbo.MetaDataDefinitions AS def ON def.ID = data.DefinitionID
LEFT OUTER JOIN dbo.MetaDataLookup AS lu ON lu.LookupType = def.Type AND lu.LookupKey = data.DataValue
WHERE data.TableID = 1
In terms of update ability, the only thing I would ever create, update or delete would be in the MetaData table. The definitions and Lookup values would never change (at least from this part of the application). Is mapping the "MetaDataLookup" directly to the MetaData model possible? If so, can someone point me in the right direction of what I should be looking at?
Thanks!

I came up with a workaround that seems to be working and might take some of the complexity out. Instead of trying to handle the complex joins in a ClassMap, I built a view in Sql Server that does this for me. In my application, I built a new Model and ClassMap for the view. I haven't implemented any update logic yet, but I think I'll have the update logic work directly on the MetaData model, while the read logic (which needs everything joined together) will use the new MetaDataView model.
I'm still curious if complex joins like this are possible in Fluent NHibernate, but for now this solution seems to be working for me.

Problem Deleting with Parent/Child

I have an issue when deleting a child record from the session. Here are the entities i have defined:
public class ReportedData
{
public virtual int ReportedDataID { get; set; }
public virtual ReportedDataTypes Type { get; set; }
public virtual string Reason { get; set; }
public virtual IList<ArticleCommentReported> ArticleCommentsReported { get; private set; }
public virtual IList<ForumPostReported> ForumPostsReported { get; private set; }
public ReportedData()
{
ArticleCommentsReported = new List<ArticleCommentReported>();
ForumPostsReported = new List<ForumPostReported>();
}
}
public class ArticleCommentReported : ReportedData
{
public virtual ArticleComment Comment { get; set; }
}
public class ForumPostReported : ReportedData
{
public virtual ForumPost Post { get; set; }
}
With the following fluent mapping:
public ReportedDataMap()
{
Table("ReportedData");
Id(x => x.ReportedDataID);
Map(x => x.Type, "TypeID");
Map(x => x.Reason);
HasMany(x => x.ArticleCommentsReported)
.KeyColumn("ReportedDataID")
.Inverse()
.Cascade.All();
HasMany(x => x.ForumPostsReported)
.KeyColumn("ReportedDataID")
.Inverse()
.Cascade.All();
}
public class ArticleCommentReportedMap : SubclassMap<ArticleCommentReported>
{
public ArticleCommentReportedMap()
{
Table("ArticleCommentsReported");
KeyColumn("ReportedDataID");
References(x => x.Comment, "CommentID");
}
}
public class ForumPostReportedMap : SubclassMap<ForumPostReported>
{
public ForumPostReportedMap()
{
Table("ForumPostsReported");
KeyColumn("ReportedDataID");
References(x => x.Post, "PostID");
}
}
Now say i try the following (i have added comments to help you understand what's going on):
// Loop over the reported data (this is my view model and not my actual model which contains an extra property for the action they wish to carry out)
foreach (var reportedData in model)
{
// If the action is leave then do nothing (else we always delete the reported data)
if (reportedData.Action != ReportedDataActions.Leave)
{
// Switch over the type since we need to make sure it deletes the article comment or post if the action is set to delete
switch (reportedData.Type)
{
case ReportedDataTypes.ArticleComment:
var reportedComment = _context.Repository<ArticleCommentReported>().GetByID(reportedData.ReportedDataID);
if (reportedData.Action == ReportedDataActions.Delete)
_context.Repository<ArticleComment>().Delete(reportedComment.Comment);
_context.Repository<ArticleCommentReported>().Delete(reportedComment);
break;
case ReportedDataTypes.ForumPost:
var reportedPost = _context.Repository<ForumPostReported>().GetByID(reportedData.ReportedDataID);
if (reportedData.Action == ReportedDataActions.Delete)
_forumService.DeletePost(reportedPost.Post);
_context.Repository<ForumPostReported>().Delete(reportedPost);
break;
}
}
}
_context.Commit();
When the user trys to delete a forum post (the Action against the reported data is set to delete) it throws the following error:
Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [ForumPostReported#2]
I could probably set some mapping up to automatically delete the post/comment once the reported data is deleted but i only want to delete the post/comment if the action is set to delete.
I'd appreciate it if someone could help. Thanks

Problem solved! I just had to delete the reported item first. Seems kinda backwards but it works and that's all i care.

Getting Data from all tables instead of one with HQL Query that should only get 1 table's data

I have created 3 tables in my database and put data into them. The 3 tables all have foreign keys joining them together. Below are the table classes and there mappings. When I run the query listed at the end I get IList<> of the objects and they have the data from all 3 tables. However, my HQL query is only from the top most table. How can I get back just the results from the top most table?
These are my classes:
public class Technology
{
public virtual int Id { get; private set; }
public virtual string Name { get; set; }
public virtual int SortOrder { get; set; }
public virtual string Abbreviation { get; set; }
public virtual IList<TechnologyDescription> TechnologyDescriptions { get; private set; }
public Technology()
{
TechnologyDescriptions = new List<TechnologyDescription>();
}
public virtual void AddTechnologyDescription(TechnologyDescription technologyDescription)
{
technologyDescription.Technology = this;
TechnologyDescriptions.Add(technologyDescription);
}
}
public class TechnologyDescription
{
public virtual int Id { get; private set; }
public virtual Technology Technology { get; set; }
public virtual string Description { get; set; }
public virtual DescriptionType DescriptionType { get; set; }
}
public class DescriptionType
{
public virtual int Id {get; private set;}
public virtual string Type { get; set; }
}
These are my mapping objects:
public class TechnologyMap : ClassMap<Technology>
{
public TechnologyMap()
{
Id(x => x.Id);
Map(x => x.Name);
Map(x => x.SortOrder);
Map(x => x.Abbreviation);
HasMany(x => x.TechnologyDescriptions)
.Inverse()
.Cascade.All();
}
}
public class TechnologyDescriptionMap : ClassMap<TechnologyDescription>
{
public TechnologyDescriptionMap()
{
Id(x => x.Id);
References(x => x.Technology);
Map(x => x.Description);
References(x => x.DescriptionType);
}
}
public class DescriptionTypeMap : ClassMap<DescriptionType>
{
public DescriptionTypeMap()
{
Id(x => x.Id);
Map(x => x.Type);
}
}
And this is my HQL code:
IQuery q = session.CreateQuery("from Technology T");
IList technologies = q.List();

I don't know if it is possible using HQL, but using NHibernate's Criteria API, you can do this:
ICriteria criteria = session.CreateCriteria (typeof(Technology));
criteria.SetFetchMode ("TechnologyDescriptions", FetchMode.Lazy);
var list = criteria.List<Technology>();
However, this is probably not really what you want. The TechnologyDescriptions won't be fetched right now, but they will be fetched once you access them (that is: the first time you call the TechnologyDescriptions property).
When working with NHibernate, you shouldn't think in terms of 'data'. Rather, you should think in terms of 'entities'.
When retrieving an entity, you want to retrieve the entity entirly (directly, or in a lazy fashion). It is not possible to retrieve an entity partially, and this is quite obvious;
What should NHibernate do with an entity that you've retrieved partially, when you try to save that entity ?
Something else that pops in my mind:
I suppose you want to retrieve the Technologies, and nothing related because you want to display them in an overview or something like that ?
In such case, you should take a look at 'Transformations'.
You could for instance create an additional class which is called TechnologyView, which looks like this:
public class TechnologyView
{
public int Id
{
get;
private set;
}
public string Name
{
get;
private set;
}
public string Abbreviation
{
get;
private set;
}
private TechnologyView()
{
// Private constructor, required for NH
}
public TechnologyView( int id, string name, string abbreviation )
{
this.Id = id;
this.Name = name;
this.Abbreviation = abbreviation;
}
}
Once you've done this, you must inform NHibernate about the existance of this class.
You do this by Importing the class in an hbm.xml file for instance . (I do not know how to do it using Fluent).
<import class="MyNamespace.TechnologyView" />
After that, you can create a query (using HQL or Criteria) which retrieves TechnologyView instances. NHibernate is smart enough to generate a performant SQL query.
using HQL:
IQuery q = s.CreateQuery ("select new TechnologyView (t.Id, t.Name, t.Abbreviation) from Technology t");
using Criteria:
ICriteria criteria = s.CreateCriteria (typeof(Technology));
criteria.SetResultTransformer (Transformers.AliasToBean (typeof(TechnologyView));
var result = criteria.List<TechnologyView>();

I think what you're looking for is for the TechnologyDescriptions to be lazy loaded. That way the descriptions get loaded from the database only when they are accessed (NHibernate will issue a second db query. Note that this can lead to N+1 selects in some situations and you might prefer the all at once query depending on the usage.)
By NHibernate xml mappings default to lazy loading of collections. In the past it seems that the Fluent NHibernate did not have the same default. You need to add .LazyLoad() to the mapping.
Recently it looks like lazy loading has become the default fluent mapping:
Is the default behavior with Fluent NHibernate to lazy load HasMany<T> collections?