I am new to nhibernate and using it firsttime with .net2.0
I am trying to do a insert .
Any help or suggestion to do it different way is a welcome.

I have two tables Employee and Emp_Relations
Employee (EmpNum(PK),Age,FirstName,LAstname)
Emp_Relations(R_ID(PK indentity),EmpNum,R_Fname)

I have two classes


public class Employee
{
#region Private
private int _empnum;
private int _age;
private Name _name ;

private IList<EmpDependent> _dependents = new List<EmpDependent>();

#endregion

#region Constructor
public Employee()
{
_name = new Name();
}
#endregion

#region Public properties

public virtual int EmpNum
{
get{return _empnum;}
set{_empnum=value;}
}
public virtual int Age
{
get{return _age;}
set{_age=value;}
}
public virtual string EmpName
{
get{return _name.CompleteName;}

}
public virtual Name Name
{
get{return _name;}
set { _name = value; }
}

public virtual void AddDependent(EmpDependent d)
{
_dependents.Add(d);
}
private IList<EmpDependent> Dependents
{
get { return _dependents; }
set { _dependents = value; }
}




#endregion


}

Second class
public class EmpDependent
{
#region Private
private int _id;
private int _empnum;
private string _fname;

#endregion
#region Constructor
public EmpDependent(string fname)
{

_fname = fname;
}
public EmpDependent()
{

}
#endregion

public virtual int ID
{
get { return _id; }
set { _id = value; }

}
public virtual string Fname
{
get{return _fname;}
set{_fname = value;}
}
public virtual int EmpNum
{
get { return _empnum; }
set { _empnum = value; }
}
}



Hibernate version:1.2.0.4000

Mapping documents:
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name ="DomainModel.Employee,DomainModel" table="Employee">
<id name ="EmpNum" type ="int">
<generator class="native" />
</id>

<property name="Age" column ="age" type="int" />
<component name ="Name" class="DomainModel.Name,DomainModel">
<property name ="FirstName" column ="FirstName" type ="string" length ="50" />
<property name ="LastName" column ="LastName" type ="string" length ="50" />

</component>

<set name="Dependents" inverse="true" lazy="true">
<key column="EmpNum"/>
<one-to-many class="DomainModel.EmpDependent,DomainModel"/>
</set>
</class>


<class name="DomainModel.EmpDependent,DomainModel" table ="Emp_Relations" >
<id name="ID" type ="int" column ="R_ID">
<generator class="native"/>
</id>
<property name="Fname" type ="string" column ="R_Fname" />
<property name="EmpNum" type ="int" column ="EmpNum" />
<many-to-one name="EmpNum" class="DomainModel.Employee,DomainModel" column="EmpNum" not-null="true"/>
</class>


</hibernate-mapping>



Full stack trace of any exception that occurs:
Test method UnitTest.EmployeeRepositoryTest.AddEmployee threw exception: NHibernate.ADOException: Could not save object ---> System.InvalidCastException: Unable to cast object of type 'System.Collections.Generic.List`1[DomainModel.EmpDependent]' to type 'Iesi.Collections.Generic.ISet`1[DomainModel.EmpDependent]'..

Name and version of the database you are using:
SQlServer 2005


Thanks

Try using a bag instead of the set to map your collection. If you use set, your collection needs to be of type ISet.

LH

If I use bag then I get following error

Test method UnitTest.EmployeeRepositoryTest.AddEmployee threw exception: NHibernate.MappingException: Invalid mapping information specified for type DomainModel.Employee, check your mapping file for property type mismatches ---> System.InvalidCastException: Unable to cast object of type 'NHibernate.Collection.Generic.PersistentGenericBag`1[DomainModel.EmpDependent]' to type 'System.Collections.Generic.List`1[DomainModel.EmpDependent]'..

It gives me casting error.

I did some changes to my code.Earlier I was trying to make a bidirectional but I changed mapping and inserting simple one to many the way it is mentioned in help document. I am using list now in the mapping file and defined an index column too.
Here is
Changed Employee class
public class Employee
{
#region Private
private int _empnum;
private int _age;
private Name _name ;

private List<EmpDependent> _dependents = new List<EmpDependent>();

#endregion

#region Constructor
public Employee()
{
_name = new Name();
}
#endregion

#region Public properties

public virtual int EmpNum
{
get{return _empnum;}
set{_empnum=value;}
}
public virtual int Age
{
get{return _age;}
set{_age=value;}
}
public virtual string EmpName
{
get{return _name.CompleteName;}

}
public virtual Name Name
{
get{return _name;}
set { _name = value; }
}

// public virtual void AddDependent(EmpDependent d)
// {
// _dependents.Add(d);
// }
public virtual List<EmpDependent> Dependents
{
get { return _dependents; }
set { _dependents = value; }
}




#endregion


}
Changed EmployeeDependent class

public class EmpDependent
{
#region Private
private int _id;
//private int _empnum;
private string _fname;
private Employee _employee;

#endregion
#region Constructor
public EmpDependent(string fname)
{

_fname = fname;
}
public EmpDependent()
{

}
#endregion

public virtual int ID
{
get { return _id; }
set { _id = value; }

}
public virtual string Fname
{
get{return _fname;}
set{_fname = value;}
}
//public virtual Employee Employee
//{
// get { return _employee; }
// set { _employee = value; }
//}

}
mapping file look like
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name ="DomainModel.Employee,DomainModel" table="Employee">
<id name ="EmpNum" type ="int">
<generator class="native" />
</id>

<property name="Age" column ="age" type="int" />
<component name ="Name" class="DomainModel.Name,DomainModel">
<property name ="FirstName" column ="FirstName" type ="string" length ="50" />
<property name ="LastName" column ="LastName" type ="string" length ="50" />

</component>

<list name="Dependents" inverse="true" lazy="true">
<key column="EmpNum"/>
<index column="EmpNum" />
<one-to-many class="DomainModel.EmpDependent,DomainModel"/>
</list>
</class>


<class name="DomainModel.EmpDependent,DomainModel" table ="Emp_Relations" >
<id name="ID" type ="int" column ="R_ID">
<generator class="native"/>
</id>
<property name="Fname" type ="string" column ="R_Fname" />

<!--
<many-to-one name="Employee" class="DomainModel.Employee,DomainModel" column="EmpNum" not-null="true"/>
-->
</class>
</hibernate-mapping>

Now error coming is
Test method UnitTest.EmployeeRepositoryTest.AddEmployee threw exception: NHibernate.MappingException: Repeated column in mapping for collection: DomainModel.Employee.Dependents column: EmpNum.

Use IList<T> instead of List<T>. It's a requirement of NHibernate due to lazy loading and all that fun stuff.

If I use IList<t>

then I cannot use Ilist<T> = new IList<t>

So if I use IList<t> _dependents

and use

public virtual IList<EmpDependent> Dependents
{
get { return _dependents; }
set { _dependents = value; }
}

So when I execute

session.save(emp)

it gives me null reference error.

On construction (or in your getter, upon determining that the IList is null) initialize your IList to a List. NH will change it to the collection class it requires for persistent bags when it needs to.