NMemory Create Relation

Description

TableCollection.CreateRelation method creates a relationship between two tables when you want to associate rows of one table with rows of another table. It takes the following arguments.

• primaryIndex: An IIndex that specifies the primary key.
• foreignIndex: An IIndex that specifies the foreign key.
• convertForeignToPrimary: A function to convert a foreign key to the corresponding primary key.
• convertPrimaryToForeign: A function to convert a primary key to the corresponding foreign key.
• relationOptions: An RelationOptions that specifies options of a relation.

To create an index, NMemory provides Table.CreateIndex method which creates a new index in a table and it takes two arguments.

• indexFactory: The index factory.
• keySelector: The expression representing the definition of the index key.

var memberIndex = members.CreateIndex(
    new RedBlackTreeIndexFactory<Member>(), 
    m => m.GroupId);

this.Tables.CreateRelation(
    groups.PrimaryKeyIndex, 
    memberIndex, 
    x => x, 
    x => x);

Try it

The columns you choose for the foreign key must have the same data type of the primary columns they correspond to.