Free Trial

Safari Books Online is a digital library providing on-demand subscription access to thousands of learning resources.


  • Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint
Share this Page URL
Help

4. Exploring EDM Queries in Greater Dept... > Retrieving a Single Entity with GetO...

Retrieving a Single Entity with GetObjectByKey

The ObjectContext.GetObjectByKey method and its counterpart, TryGetObjectByKey, provide a way to query for an object without having to construct and execute a query. However, this has a notable twist. The runtime will first look in the existing instantiated objects to see whether the object has already been retrieved. If it is found, this is what will be returned. If not, the query to the data store will be executed automatically and the object will be returned.

GetObjectByKey takes an EntityKey type that defines what object to retrieve based on its EntitySet, its key property name, and the value of that property. For example, EntityKey("PEF.Contacts","ContactID",5) defines an object in the Contacts EntitySet with a ContactID value of 5. Once the EntityKey has been created, GetObjectByKey(myEntityKey) will return the object either from memory or from the database.


  

You are currently reading a PREVIEW of this book.

                                                                                                                    

Get instant access to over $1 million worth of books and videos.

  

Start a Free 10-Day Trial


  
  • Safari Books Online
  • Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint