CODEWITHSUNDEEP
nhibernatemappingforeign-keys
daxnet
daxnet

Reputation: 103

How can I map a foreign key ID column (property) in NHibernate?

I have a question about how to map a foreign key ID with NHibernate mapping file. eg. I have the following classes: 

class Topic {
  public long ID {get; set;}  
  public string Name {get; set;}  
}  

class Post {  
  public long ID {get; set;}  
  public string Title {get; set;}  
  public string Content {get; set;}  
  public long TopicID {get; set;} // This is the FK refers to the Topic entity
}

The Post entity doesn't reference the Topic directly, it only references the Topic by the TopicID as show above. However seems that NHibernate <many-to-one> mapping will only map the Topic as an entity in the Post, but I what I want is the TopicID FK, not the Topic entity. Could anybody help me on this?

Many thanks!

Upvotes: 2

Views: 2298

Answers (2)

Joe Alfano
Joe Alfano

Reputation: 10289

If you just want a property in your Post mapping that contains the value of the TopicID field, then just map it as a simple property:

<property name="TopicID" column="TopicID" type="long" />

If you want it mapped as an object, then use a many-to-one mapping:

<many-to-one name="Topic" column="TopicID" class="Topic"  />

Upvotes: 1

Andrew Shepherd
Andrew Shepherd

Reputation: 45222

You can just declare the TopicID as a property, and not a many-to-one.

<property name="TopicID" column="TopicID" type="Int64" />

Upvotes: 0

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