Nhibernate Many-to-Many bridge table Keep to be empty

Question

I have two tables with a many-to-many relation with a bridge table.

User Class Mapping :

<class name="MatrixCore.User" table="MatrixUser" lazy="false">
    <id name="ID" column="ID" unsaved-value="0">
      <generator class="native"/>
    </id>
    <property name="FirstName"/>
    <property name="LastName"/>
    <property name="UserName"/>
    <property name="Password"/>
    <many-to-one name="UserType" class="MatrixCore.UserType" />
    <set name="Projects" table="UserInProject" cascade="All">
      <key column="MatrixUser_ID"/>
      <many-to-many class="Project" column="Project_ID"/>
    </set>
  </class>

Project class mapping :

<class name="MatrixCore.Project" table="Project" lazy="false">
   <id name="ID" column="ID" unsaved-value="0">
     <generator class="native"/>
   </id>
   <property name="Name" />
   <property name="Acronym"/>
   <property name="StartDate"/>
   <property name="EndDate"/>
   <set name="Users" table="UserInProject" cascade="All">
     <key column="Project_ID"/>
     <many-to-many class="User" column="MatrixUser_ID" />
   </set>
</class>

the classes implementations are too simple each class have a collection of the other. I am trying to insert records in the tables the bridge table keep to be empty.

    ICollection<Project> ps = new HashSet<Project>() { project};

            UserType tp = (UserType)session.Get("UserType", 1);
            User u = new User()
            {
                FirstName = "Hussein",
                LastName = "Hussein",
                UserName = "Hussein",
                Password = "welcome",
                UserType = tp,
                Projects = ps
            };

            session.Save(u);

You should really create an interim table (ProjectUsers) that references both the Project and the User to prevent the many to many relationship :) — Mathew Thompson, May 01 '12 at 21:11

Sleiman Jneidi · Accepted Answer · 2012-05-04T18:02:56.947

2

try this mapping for user class

<set name="Projects" table="UserInProject" inverse="true" cascade="save-update" lazy="false">
  <key column="MatrixUser_ID" />
  <many-to-many class="Project" column="Project_ID"/>
</set>

and for Project Class

<set name="Users" table="UserInProject" cascade="save-update" lazy="false">
  <key column="Project_ID"  />
  <many-to-many class="User" column="MatrixUser_ID"/>
</set>

edited May 04 '12 at 18:02

answered May 03 '12 at 09:16

Sleiman Jneidi

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Thanks sleiman it works just fine can you explain how the inverse attribute would solve the problem I am a little bit stunned. – Hussein Zawawi May 04 '12 at 18:12
2

[This would be helpful](http://stackoverflow.com/questions/713637/inverse-attribute-in-nhibernate) – Sleiman Jneidi May 04 '12 at 18:16

score 0 · Answer 2 · answered May 01 '12 at 21:04

0

You need to add the user to the Users property in each one of the Projects.

Add the following loop before the Save -

foreach (Project project in u.Projects)
{
   project.Users.Add(u);
}

answered May 01 '12 at 21:04

Mr Mush

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Nhibernate Many-to-Many bridge table Keep to be empty

2 Answers2