nHibernate: How to setup a one-to-many relation with same composite id without changing the database?

[ArnoDeckx]

I want to setup a one-to-many relation between 2 classes. These classes both have a composite Id, that is the same except for one column. But I get an error because my Id's have the same name.

This topic actually describes my problem very well, but the answer is useless to me because I can not change the name of the column in the database.

here are the classes:

public class Parent
{
public string A { get; set; }
public string B { get; set; }
public string C { get; set; }
public List Children { get; set; }
public string Data { get; set; }
}
public class Child
{
public string A { get; set; }
public string B { get; set; }
public string C { get; set; }
public string D { get; set; }
public Parent Parent { get; set; }
public string Data { get; set; }
}

public class ParentMap : ClassMap
{
public ParentMap()
{
CompositeId()
.KeyProperty(x => x.A)
.KeyProperty(x => x.B)
.KeyProperty(x => x.C);
Map(x => x.Data);
HasMany(x => x.Children)
.KeyColumns.Add("A", "B", "C");
}
}
public class ChildMap : ClassMap
{
public ChildMap()
{
CompositeId()
.KeyProperty(x => x.A)
.KeyProperty(x => x.B)
.KeyProperty(x => x.C)
.KeyProperty(x => x.D);
Map(x => x.Data);
References(x => x.Parent)
.Columns("A", "B", "C");
// Also tried adding this
// .Not.Insert()
// .Not.Update()
}
}
When I try to run this code the following exception pops up: An invalid or incomplete configuration was used while creating a SessionFactory. Check PotentialReasons collection, and InnerException for more detail.

With this inner exception: Unable to build the insert statement for class Parent: a failure occured when adding the Id of the class

This inner exception has another inner exception: The column 'A' has already been added in this SQL builder Parameternaam: columnName

I have seen in the fluent-nhibernate source code that it indeed adds no information about the table the column belongs to in the list of columns in the insert statement constructor. Is this a bug or can this be achieved another way? Preferably without changes to the database.

[crenan]

You could try something like:

public class Parent
{
    public virtual string A { get; set; }
    public virtual string B { get; set; }
    public virtual string C { get; set; }
    public virtual List Children { get; set; }
    public virtual string Data { get; set; }
}

public class Child
{
    public virtual Parent Parent { get; set; }
    public virtual string D { get; set; }
    public virtual string Data { get; set; }
}

public class ParentMap : ClassMap
{
    public ParentMap()
    {
        CompositeId()
            .KeyProperty(x => x.A)
            .KeyProperty(x => x.B)
            .KeyProperty(x => x.C);
        Map(x => x.Data);
        HasMany(x => x.Children)
            .KeyColumns.Add("A", "B", "C");
    }
}

public class ChildMap : ClassMap
{
    public ChildMap()
    {
        CompositeId()
            .KeyReference(x => x.Parent, "A", "B", "C")
            .KeyProperty(x => x.D);
        Map(x => x.Data);
    }
}

Don't forget to override Equals and GetHashCode if you use CompositeId().

[yusianglin11010]

It worked! You saved my day!

Just for reference, if you need to reference the parent table from a child, it might look something like this:

         References(x => x.Parent)
             .Columns("A", "B", "C") 
             .LazyLoad();