MapKey Class
NPersistence Reference Guide
Specifies the map key for associations of type Dictionary<(Of <(<'TKey, TValue>)>)> when the map key is itself the primary key or a persistent field or property of the entity that is the value of the map.

If a persistent field or property other than the primary key is used as a map key then it is expected to have a uniqueness constraint associated with it.

The MapKeyClass annotation is not used when MapKey is specified and vice versa.

Examples

CopyC#
Example 1:

[Entity]
public class Department {
    ...
    [OneToMany(mappedBy="department")]
    [MapKey]  // map key is primary key
    public Dictionary<Integer, Employee> getEmployees() {... }
    ...
}

[Entity]
public class Employee {
    ...
    [Id] Integer getEmpId() { ... }
    [ManyToOne]
    [JoinColumn(name="dept_id")]
    public Department getDepartment() { ... }
    ...
}

Example 2:

[Entity]
    public class Department {
    ...
    [OneToMany(mappedBy="department")]
    [MapKey(name="name")]
    public Dictionary<String, Employee> getEmployees() {... }
    ...
}

[Entity]
    public class Employee {
    [Id] public Integer getEmpId() { ... }
    ...
    [ManyToOne]
    [JoinColumn(name="dept_id")]
    public Department getDepartment() { ... }
    ...
}

Namespace: NPersistence
Assembly: NPersistence (in NPersistence.dll) Version: 2.0.0.0 (2.0.0.0)

Syntax

   
 C# 
public sealed class MapKey : Attribute

Members

         
 All Members  Constructors   Fields  
 Public

 Protected
 Instance

 Static 
 Declared

 Inherited
 XNA Framework Only 

 .NET Compact Framework Only 

 MemberDescription
MapKey()()()()
Initializes a new instance of the MapKey class
Name
(Optional) The name of the persistent field or property of the associated entity that is used as the map key. Default: If the name element is not specified, the primary key of the associated entity is used as the map key. If the primary key is a composite primary key and is mapped as IdClass, an instance of the primary key class is used as the key.

Inheritance Hierarchy

System..::..Object
  System..::..Attribute
    NPersistence..::..MapKey

See Also