I've found a number of posts about this but none seem to help me directly. Also there seems to be confusion about solutions working or not working during different stages of FluentNHibernate's development.
I have the following classes:
public class MappedClass
{
...
}
public enum MyEnum
{
One,
Two
}
public class Foo
{
...
public virtual IDictionary<MappedClass, MyEnum> Values { get; set; }
}
My questions are:
Will I need a separate (third) table of MyEnum?
How can I map the MyEnum type? Should I?
What should Foo's mapping look like?
I've tried mapping HasMany(x => x.Values).AsMap("MappedClass")...
This results in: NHibernate.MappingException : Association references unmapped class: MyEnum
It looks like this questions is a duplicate of Fluent code for mapping an IDictionary<SomeEntity, int>?. The solution was to use hbm.xml to map a ternary association table. It looks like at the time FluentNHibernate's AsTernaryAssocation() method only worked for entity types. I can't tell if this has changed, or if it is a planned feature.
Related
I´m using Fluent Nhibernate with automapping and having problem setting up a bi-directional HasMany relationship because of my current inheritance.
I simplified version of my code looks like this
public abstract class BaseClass
{
public BaseClass Parent { get; set; }
}
public class ClassA : BaseClass
{
public IList<ClassB> BChilds { get; protected set; }
public IList<ClassC> CChilds { get; protected set; }
}
public class ClassB : BaseClass
{
public IList<ClassD> DChilds { get; protected set; }
}
public class ClassC : BaseClass
{
}
public class ClassD : BaseClass
{
}
Every class can have one parent and some parents can have childs of two types. I´m using table-per-type inheritance which result in the tables
"BaseClass"
"ClassA"
"ClassB"
"ClassC"
"ClassD"
To get a working bi-directional mapping I have made the following overrides
(one example from ClassA)
mapping.HasMany<BaseType>(x => x.BChilds).KeyColumn("Parent_Id");
mapping.HasMany<BaseType>(x => x.CChilds).KeyColumn("Parent_Id");
This works fine on classes with only one type of children, but ClassA with two child types will get all subtypes of BaseType in each list which ofcourse will end up in an exception. I have looked at two different workarounds tho none of them feels really sufficient and I really believe there is a better way to solve it.
Workaround 1: Point to the concrete subtype in the HasMany mapping. (Updated with more info)
mapping.HasMany<ClassB>(x => x.BChilds).KeyColumns("Parent_Id");
(BaseType replaced with ClassB)
With this mapping NHibernate will in some cases look in the ClassB table for a column named Parent_Id, obviously there is no such column as it belongs to the BaseClass table. The problem only occurs if you add a statement based on BChilds during a ClassA select. e.g loading an entity of ClassA then calling ClassA.BChilds seems to work, but doing a query (using NhibernateLinq) something like
Query<ClassA>().Where(c => c.BChilds.Count == 0)
the wrong table will be used. Therefore I have to manually create a new column in this table with the same name and copy all the values. It works but it´s risky and not flexible at all.
Workaround 2: Add a column to the BaseClass that tells the concrete type and add a where statement to the HasMany mapping.
(after my update to workaround1 I´m no longer sure if this could be a workable solution)
By adding a column they same way as it´s done when using table-per-hierarchy inheritance with a discriminatorValue. i.e BaseType table will get a new column with a value of ClassA, ClassB... Tho given how well NHibernate handles the inheritance overall and by reading the NHibernate manual I believe that the discriminator shouldn´t be needed in a table-per-type scenario, seems like Nhibernate already doing the hardpart and should be able to take care of this in a clean way to without adding a new column, just can´t figure out how.
What's your base class mapping and what does your subclass map look like?
You should be able to do
mapping.HasMany(x => x.BChilds);
And with the correct mapping, you shouldn't have a problem.
If it's fluent nhibernate, look into
UseUnionSubclassForInheritanceMapping();
I would like to map an Nhibernate many-to-one property to an interface like the following if that is possible:
public
public interface IContact
{
Guid Uid { get; set; }
string FirstName {get;set;}
//etc. etc.
}
I am fairly sure I can only map to concrete types but maybe somebody can point out a way?
It's all described in the docs: Chapter 8. Inheritance Mapping
Depending on the chosen strategy, you'll map the reference property as many-to-one (most cases) or any (only if you use implicit polymorphism)
You can map to an interface ... and it works exactly as it does for concrete classes.
I have a class which I would like to map as a component onto any table which contains it:
public class Time
{
public int Hours { get; set; }
public int Minutes { get; set; }
public int Seconds { get; set; }
}
I would like to store this class as a bigint in the database - the same as how TimeSpan is stored but my class has completely different behaviour so I decided to create my own.
I'm using FLH's automapper and have this class set as a component (other classes have Time as a property). I've got as far as creating an override but am not sure how to go about mapping it:
I gave it a try this way:
public class TimeMappingOverride : IAutoMappingOverride<Time>
{
public void Override(AutoMapping<Time> mapping)
{
mapping.Map(x => x.ToTimeSpan());
mapping.IgnoreProperty(x => x.Hours);
mapping.IgnoreProperty(x => x.Minutes);
mapping.IgnoreProperty(x => x.Seconds);
}
}
But got this error:
Unable to cast object of type 'System.Linq.Expressions.UnaryExpression' to type 'System.Linq.Expressions.MethodCallExpression'.
How should I go about this?
Details of components can be found here: http://wiki.fluentnhibernate.org/Fluent_mapping#Components
But first of all, you can't map a method.
Assuming you change ToTimeSpan() to a property AsTimeSpan, there are two ways to do it, only the harder of which will work for you because you are using automapping:
Create a ComponentMap<Time> -- once done, your existing mapping will just work. This is not compatible with automapping.
Declare the component mapping inline:
mapping.Component(x => x.AsTimeSpan, component => {
component.Map(Hours);
component.Map(Minutes);
component.Map(Seconds);
});
You'll have to do this every time, though.
Of course, this doesn't address "I would like to store this class as bigint…"
Are you saying you want to persist it as seconds only? If so, scratch everything at the top and again you have two options:
Implement NHibernate IUserType (ugh)
Create a private property or field that stores the value as seconds only, and wire only this up to NHibernate. The getters and setters of the pubic properties will have to convert to/from seconds.
I personally haven't worked with AutoMappings yet, but my suggestion would be to look into NHibernate's IUserType to change how a type is being persisted. I believe that's a cleaner way of defining your custom mapping of Time <-> bigint.
Reading the code above, Map(x => x.ToTimeSpan()) will not work as you cannot embed application-to-database transformation code into your mappings. Even if that would be possible, the declaration misses the transformation from the database to the application. A IUserType, on the other hand, can do custom transformations in the NullSafeGet and NullSafeSet methods.
NHibernate seems to support a special case of one to one mapping (That doesn't require a 1-m mapping on each side of the relationship).
See this article by Ayende:
http://nhibernate.info/blog/2009/04/18/nhibernate-mapping-lt-one-to-one-gt.html
I have no idea how to specify this in Fluent NHibernate though - is this possible?
Ah, just found from a helpful person in the Fluent group that I can use
HasOne(x => x.Cover);
Missed it somehow before :/
One scenario is with subclasses. You can specific a table per hierarchy or per class.
You would need to override for the per hierarchy something like below:
public class UserMap : IAutoMappingOverride<User>
{
public void Override(AutoMapping<User> mapping)
{
mapping.DiscriminateSubClassesOnColumn<int>("UserType");
}
}
public void Override(AutoMapping<Person> mapping)
{
mapping.Table("Persons");
DiscriminatorValue((int)UserTypes.Person);
}
I have a class called Entry. This class as a collection of strings called TopicsOfInterest. In my database, TopicsOfInterest is represented by a separate table since it is there is a one-to-many relationship between entries and their topics of interest. I'd like to use nhibernate to populate this collection, but since the table stores very little (only an entry id and a string), I was hoping I could somehow bypass the creation of a class to represent it and all that goes with (mappings, configuration, etc..)
Is this possible, and if so, how? I'm using Fluent Nhibernate, so something specific to that would be even more helpful.
public class Entry
{
private readonly IList<string> topicsOfInterest;
public Entry()
{
topicsOfInterest = new List<string>();
}
public virtual int Id { get; set; }
public virtual IEnumerable<string> TopicsOfInterest
{
get { return topicsOfInterest; }
}
}
public class EntryMapping : ClassMap<Entry>
{
public EntryMapping()
{
Id(entry => entry.Id);
HasMany(entry => entry.TopicsOfInterest)
.Table("TableName")
.AsList()
.Element("ColumnName")
.Cascade.All()
.Access.CamelCaseField();
}
}
I had a similar requirement to map a collection of floats.
I'm using Automapping to generate my entire relational model - you imply that you already have some tables, so this may not apply, unless you choose to switch to an Automapping approach.
Turns out that NHibernate will NOT Automap collections of basic types - you need an override.
See my answer to my own question How do you automap List or float[] with Fluent NHibernate?.
I've provided a lot of sample code - you should be able to substitute "string" for "float", and get it working. Note the gotchas in the explanatory text.