EntitySpaces™ Hierarchical Support

The EntitySpaces Hierarchical Template uses the foreign keys in your database to automatically build the hierarchical object model. First the standard templates generate the Collections and Entities then the Hierarchical Template generates a partial class that hooks them all up in a hierarchical fashion.

EntitySpaces will automatically save down the hierarchical tree from Parent to Child.  This process is iterative, so calling save on an EntitySpaces Northwind CustomersCollection (custs.Save()) will, also, save all changes to custs.OrdersCollectionByCustomerID, which will in turn save any changes to OrderDetailsCollectionByOrderID. If a Parent has an auto-incrementing key, then that is retrieved and filled in to the foreign key column for you. Everything is handled in the right order, so a Parent will not be deleted before the related Children, or added after related Child records. This prevents foreign key constraints from being violated in the database.

To prevent endless loops, EntitySpaces does not automatically save up the hierarchical tree. To help you determine whether a particular hierarchical sub-object is upstream or down, the default generated names for upstream sub-objects will start with the prefix "UpTo".

Many-To-One

Let's start out by looking at a Many To One example using the Northwind Products table which has a CategoryID that points to the product's category. The code below loads a product, then accesses its category sub-object printing the name.  A many to one uses an Entity to represent the nested sub-object.

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Zero-To-Many

A Zero To Many uses a collection to represent the nested sub-object. Here we are going to loop through all the OrderDetails for a given Product. This example raises the prices by 10%.

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Now we are going to add an OrderDetails record to this Products data.

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Many-To-Many

A Many-to-Many like the Zero-to-Many uses a collection to represent the nested sub-object. There are two new methods on a Many-To-Many and they are Associate and Dissociate. EntitySpaces implements the Many-to-Many in such a way that you never actually see the linking table. However, there are EntitySpaces objects for the linking table, they are just hidden away to make your life easier.

In this example we are going to loop through all of the Territories for a given Employee. Behind the scenes there is set of EntitySpaces classes to represent the EmployeeTerritories table however they are not exposed though the programmer can use them at will whenever desired.

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You can also associate and dissociate Territories as follows.

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We hope this provides you an idea of how the EntitySpaces Hierarchical Model is used.