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   How to: Access Data in SQL Query Results
   How to: Bind an XPCollection to a LookUp
   How to: Bind an XPCollection to Standard Controls
   How to: Bind an XPCollection to the DataGrid
   How to: Bind an XPCollection to the Grid
   How to: Build Complex Criteria
   How to: Build Simple Criteria
   How to: Change Inheritance Mapping
   How to: Connect to a SQL Server
   How to: Connect to SQL Azure
   How to: Connect XPO to a Database Other than MS SQL or MS Access
   How to: Control Automatic Saving of Objects when Editing in a Grid
   How to: Create an Aggregated Object
   How to: Delay Property Loading
   How to: Filter By DateTime Values
   How to: Filter Persistent Objects by Type
   How to: Handle Persistent Object Initialization
   How to: Implement a Custom Criteria Language Function Operator
   How to: Implement a Full-Text Search
   How to: Implement Custom Functions and Criteria in LINQ to XPO
   How to: Implement Many-to-Many Relationships
   How to: Implement One-to-One Relationships
   How to: Link Classes Located in Different Assemblies
   How to: Make a Class or Property Non-Persistent
   How to: Make XPCollection Create Objects of Specific Type when They are Created via Bound Controls
   How to: Map to Custom Tables (Views) and Columns
   How to: Obtain a Collection of Persistent Objects by a Set of Their IDs
   How to: Obtain a Collection of Persistent Objects for Processing
   How to: Persist a BLOB Field
   How to: Prevent Changes in a Persistent Object from being Automatically Committed
   How to: Restore Deleted Objects
   How to: Use Pageable Collections
   How to: Use Read-Only Persistent Properties
   How to: Use the ContainsOperator for Objects in a Many-to-Many Relationship
   How to: Validate an Object
   How to: Work with Structures
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How to: Implement Many-to-Many Relationships

There are three types of relationships between objects. The type of a relationship that is created depends upon how related objects are defined. To learn about a particular relationship type, click a corresponding link below.

 

This article demonstrates how to create many-to-many relationships in databases created by XPO. If you are using XPO to map to existing databases, refer to the approach described in the Generating Persistent Objects for Existing Data Tables topic.

XPO can handle Many-to-Many relationship between objects. In the following code example, the Location class might contain several Departments and every Department can in turn span several Locations.

Important

Do not modify the XPCollection property declaration demonstrated above. Manipulating the collection or introducing any additional settings within the declaration may cause unpredictable behavior.

To create data use the following code.

The code listed above is sufficient for XPO to work properly: it will generate all necessary intermediate tables and relationships.

To use the association's name as the name of a junction table, set the AssociationAttribute.UseAssociationNameAsIntermediateTableName property to true.

Expanded See Also

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