Fluent NHibernate One to Many - Transient Instance Exception - nhibernate

Question

I am attempting to do a simple one to many mapping in fluent NHibernate, however i receive the following exception:
"NHibernate.TransientObjectException : object references an unsaved transient instance - save the transient instance before flushing or set cascade action for the property to something that would make it autosave. Type: Voter.Domain.Entities.VoteOption, Entity: Voter.Domain.Entities.VoteOption"
I have tried numerous using Cascade().All() - but this makes no difference.
Please help me to get this cascade working! Much time already wasted...
I have the following entities:
public class Vote
{
public Vote()
{
VoteOptions = new List<VoteOption>();
}
public virtual int Id { get; protected set; }
public virtual Guid VoteReference { get; set; }
public virtual string Title { get; set; }
public virtual string Description { get; set; }
public virtual DateTime ValidFrom { get; set; }
public virtual DateTime ValidTo { get; set; }
public virtual IList<VoteOption> VoteOptions { get; set; }
public virtual void AddOption(VoteOption voteOption)
{
VoteOptions.Add(voteOption);
}
public virtual void AddOptions(List<VoteOption> options)
{
foreach (var option in options.Where(option => VoteOptionAlreadyExists(option) == false))
{
VoteOptions.Add(option);
}
}
private bool VoteOptionAlreadyExists(VoteOption voteOption)
{
return VoteOptions.Any(x => x.Description == voteOption.Description);
}
}
public class VoteOption
{
public virtual int Id { get; protected set; }
public virtual string LongDescription { get; set; }
public virtual string Description { get; set; }
public virtual Vote Vote { get; set; }
}
And the following mappings:
public VoteMap()
{
Table("Vote");
Id(x => x.Id).GeneratedBy.Identity().Column("Id");
Map(x => x.VoteReference).Column("VoteReference");
Map(x => x.Title).Column("Title").Not.Nullable();
Map(x => x.Description).Column("Description").Not.Nullable();
Map(x => x.ValidFrom).Column("ValidFrom").Not.Nullable();
Map(x => x.ValidTo).Column("ValidTo").Not.Nullable();
HasMany(x => x.VoteOptions).KeyColumn("Vote_Id").Cascade.All();
}
public class VoteOptionMap : ClassMap<VoteOption>
{
public VoteOptionMap()
{
Table("VoteOption");
Id(x => x.Id).GeneratedBy.Identity().Column("Id");
Map(x => x.Description).Column("Description").Not.Nullable();
Map(x => x.LongDescription).Column("LongDescription").Not.Nullable();
References(x => x.Vote).Column("Vote_Id").Cascade.All();
}
}
And the following SQL Server database tables:
CREATE TABLE dbo.Vote
(
Id INT IDENTITY(1,1) PRIMARY KEY,
VoteReference UNIQUEIDENTIFIER NULL,
Title VARCHAR(500) NOT NULL,
[Description] VARCHAR(1000) NOT NULL,
ValidFrom DATETIME NOT NULL,
ValidTo DATETIME NOT NULL
)
CREATE TABLE dbo.VoteOption
(
Id INT IDENTITY(1,1) PRIMARY KEY,
Vote_Id INT NOT NULL,
[Description] VARCHAR(500) NOT NULL,
LongDescription VARCHAR(5000) NOT NULL
)
Implementation code is:
public void Save()
{
var vote = new Vote
{
VoteReference = new Guid(),
Title = "Events Vote",
Description = "Which event would you like to see next?",
ValidFrom = DateTime.Now.AddDays(-2),
ValidTo = DateTime.Now.AddDays(3)
};
var options = new List<VoteOption>
{
new VoteOption {Description = "What you want?", LongDescription = "Tell me all about it..."},
new VoteOption {Description = "Another option?", LongDescription = "Tell me some more..."}
};
vote.AddOptions(options);
using (var session = sessionFactory().OpenSession())
{
using (var transaction = session.BeginTransaction())
{
//This works - but undermines cascade!
//foreach (var voteOption in vote.VoteOptions)
//{
// session.Save(voteOption);
//}
session.Save(vote);
transaction.Commit();
}
}
}
private ISessionFactory sessionFactory()
{
var config = new Configuration().Configure();
return Fluently.Configure(config)
.Mappings(m => m.AutoMappings.Add(AutoMap.AssemblyOf<Vote>()))
.BuildSessionFactory();
}

Answer 1

I would say, that setting as shown above (the fluent mapping) is ok. Other words, the code I see right now, seems to be having different issue, then the Exception at the top.
The HasMany cascade setting is OK, but I would suggest to mark it as inverse (see here for more info ... NHibernate will not try to insert or update the properties defined by this join...)
HasMany(x => x.VoteOptions)
.KeyColumn("Vote_Id")
.Inverse()
.Cascade.All();
Also, the Reference should be in most case without Cascade: References(x => x.Vote).Column("Vote_Id");
Having this, and running your code we should be recieving at the moment the SqlException: *Cannot insert the value NULL into column 'Vote_Id'*
Because of the TABLE dbo.VoteOption defintion:
...
Vote_Id INT NOT NULL, // must be filled even on a first INSERT
So, the most important change should be in the place, where we add the voteOption into Vote collection (VoteOptions). We always should/must be providing the reference back, ie. voteOption.Vote = this;
public virtual void AddOption(VoteOption voteOption)
{
VoteOptions.Add(voteOption);
voteOption.Vote = this; // here we should/MUST reference back
}
public virtual void AddOptions(List<VoteOption> options)
{
foreach (var option in options.Where(option => VoteOptionAlreadyExists(option) == false))
{
VoteOptions.Add(option);
option.Vote = this; // here we should/MUST reference back
}
}
After these adjustments, it should be working ok

Answer 2

The cascade option can be set globally using Fluent NHibernate Automapping conventions. The issue that #Radim Köhler pointed out also needs to be corrected when adding items to the List.
Using global conventions:
Add a convention, it can be system wide, or more restricted.
DefaultCascade.All()
Code example:
var cfg = new StoreConfiguration();
var sessionFactory = Fluently.Configure()
.Database(/* database config */)
.Mappings(m =>
m.AutoMappings.Add(
AutoMap.AssemblyOf<Product>(cfg)
.Conventions.Setup(c =>
{
c.Add(DefaultCascade.All());
}
)
.BuildSessionFactory();
Now it will automap the cascade when saving.
More info
Wiki for Automapping
Table.Is(x => x.EntityType.Name + "Table")
PrimaryKey.Name.Is(x => "ID")
AutoImport.Never()
DefaultAccess.Field()
DefaultCascade.All()
DefaultLazy.Always()
DynamicInsert.AlwaysTrue()
DynamicUpdate.AlwaysTrue()
OptimisticLock.Is(x => x.Dirty())
Cache.Is(x => x.AsReadOnly())
ForeignKey.EndsWith("ID")
See more about Fluent NHibernate automapping conventions