A navigation property is tied to an association. An association is a named relationship between two entity types. Every association includes two association ends, which specify the entity types that are related and the cardinality rules for each end of the association.

 

 

CRUD Operations

One of the main features of OData is that it uses the existing HTTP verbs GET, PUT, POST, and DELETE against addressable resources identified in the URI.

 

Conceptually, OData is a way of performing database-style create, read, update, and delete operations on resources by using HTTP verbs.

 

 

CRUD Operations Called on Entity Sets

We have already observed how we can read the service document and the service metadata document using HTTP GET. Here we focus on how we can perform create, read, update, and delete operations.

 

The following operation can be called on entity sets:

• A GET request to read a feed, or in other words a set of entries of the same entity type as you have already seen with the Products entity set.
  
  To create a new entry of a specific entity type, you have to send a post request to the corresponding entity set. To create a new product, you just send it via post to the URI of the resource product’s entity set.
  

 

The following operation can be called on entities:

• A single entry can be read by a GET request. If you choose to modify this single entry, you can use PUT or PATCH. PUT is used for updating the whole entity. PATCH allows us to partially update the entity.
  If you want to get rid of an entity, you can just send a delete command to the self-link of the entity.
  

 

OData batching enables you to send multiple operations in a single HTTP request. You can express that all these operations must be executed on the server with an all-or-nothing logic. In an OData batch request, the payload is represented as a multipart message. A batch request is sent to the batch endpoint of an OData service. The URI of the batch endpoint is the service root URI appended by $batch.