CODEWITHSUNDEEP
c#.netnhibernate
Mike Thomsen
Mike Thomsen

Reputation: 37526

Need help doing a one-to-many relationship with NHibernate

Here are the mappings for my objects:

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                   assembly="NHibernateTest"
                   namespace="NHibernateTest.Database">
    <class name="Employer">
        <id name="Id" type="Int64" column="id" unsaved-value="0">
            <generator class="identity"/>
        </id>
        <property name="Name"/>
    </class>
</hibernate-mapping>

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                   assembly="NHibernateTest"
                   namespace="NHibernateTest.Database">
    <class name="Employee">    
        <id name="Id" type="Int64" column="id" unsaved-value="0">
            <generator class="identity"/>
        </id>
        <property name="FirstName"/>
        <property name="LastName"/>
        <property name="Email"/>
    </class>
</hibernate-mapping>

Here are the objects themselves:

namespace NHibernateTest.Database {
    public class Employee {
        public virtual long Id { get; set; }
        public virtual string FirstName { get; set; }
        public virtual string LastName { get; set; }
        public virtual string Email { get; set; }
    }

    public class Employer {
        public virtual long Id { get; set; }
        public virtual string Name { get; set; }
        public virtual IList<Employee> Employees { get; set; }
    }
}

I'm trying to use the SchemaExport utility to generate the schema, but cannot figure out how to write the mapping for the IList. It's been a long time since I've touched Hibernate for Java and am finding the documentation on one-to-many for NHibernate to be a bit difficult to follow. If someone could write that mapping, I'd be much obliged.

Upvotes: 0

Views: 632

Answers (1)

Spencer Ruport
Spencer Ruport

Reputation: 35117

I had to guess the name of the Employee table and the Employer.Id foreign key but here's how I would do it:

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                   assembly="NHibernateTest"
                   namespace="NHibernateTest.Database">
    <class name="Employer">
        <id name="Id" type="Int64" column="id" unsaved-value="0">
            <generator class="identity"/>
        </id>
        <property name="Name"/>
        <bag name="Employees" table="Employees" >
            <key column="EmployerId"></key>
            <one-to-many class="Employee"></one-to-many>
       </bag>
    </class>
</hibernate-mapping>

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                   assembly="NHibernateTest"
                   namespace="NHibernateTest.Database">
    <class name="Employee">    
        <id name="Id" type="Int64" column="id" unsaved-value="0">
            <generator class="identity"/>
        </id>
        <property name="EmployerId" />
        <property name="FirstName"/>
        <property name="LastName"/>
        <property name="Email"/>
    </class>
</hibernate-mapping>

Here's the .net code:

namespace NHibernateTest.Database {
    public class Employee {
        public Employee(Employer employer) { EmployerId = employer.Id; }
        protected Employee() {} // nHibernate needs access to a parameterless constructor.
        public virtual long Id { get; set; }
        protected virtual long EmployerId { get; set; }
        public virtual string FirstName { get; set; }
        public virtual string LastName { get; set; }
        public virtual string Email { get; set; }
    }

    public class Employer {
        public virtual long Id { get; set; }
        public virtual string Name { get; set; }
        public virtual IList<Employee> Employees { get; set; }
    }
}

Upvotes: 1

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