Querying objects after AddObject before SaveChanges?

by

To persist an entity you usually add it to it’s DbSet in the context.

For example

var bar = new Bar();
bar.Name = "foo";
var context = new Context();
context.Bars.Add(bar);

Surprisingly, querying context.Bars, the just added entity cannot be found

var howMany = context.Bars.Count(b => b.Name == "foo");
// howMany == 0

After context.SaveChanges() the same line will result 1

The DbSet seems unaware to changes until they’re persisted on db.

Fortunately, each DbSet has a Local property that acts like the DbSet itself, but it reflect all in-memory operations

var howMany = context.Bars.Local.Count(b => b.Name == "foo");
// howMany == 1

You can also use Local to add entities

context.Bars.Local.Add(bar);

and get rid of the weird behavior of Entity Framework.

More Related Contents:

  1. What’s the difference(s) between .ToList(), .AsEnumerable(), AsQueryable()?
  2. Disable lazy loading by default in Entity Framework 4
  3. ADO.NET DbContext Generator vs. ADO.NET Poco Entity Generator (ObjectContext)
  4. How to include a child object’s child object in Entity Framework 5
  5. Entity Framework 4 / POCO – Where to start? [closed]
  6. Asp.Net Web API Error: The ‘ObjectContent`1’ type failed to serialize the response body for content type ‘application/xml; charset=utf-8’
  7. The specified named connection is either not found in the configuration, not intended to be used with the EntityClient provider, or not valid
  8. Unique keys in Entity Framework 4
  9. Entity Framework 4 selective lazy loading properties
  10. Upgrade EF 4 EDMX to EF 6
  11. EF Migrations: Rollback last applied migration?
  12. EF Code First giving me error Cannot insert explicit value for identity column in table ‘People’ when IDENTITY_INSERT is set to OFF. [duplicate]
  13. Using Entity Framework with an SQL Compact Private Installation
  14. Map two different entities to the same table?
  15. How to use Entity Framework to map results of a stored procedure to entity with differently named parameters
  16. AutomaticMigrationsEnabled false or true?
  17. Compose queries across Entity Data Models
  18. Changing Inherited Types in Entity Framework
  19. ASP.NET MVC 2.0 Implementation of searching in jqgrid
  20. Code First: Independent associations vs. Foreign key associations?
  21. Entity Framework Timeouts
  22. Entity Framework 6 Code first Default value
  23. Database first create entity framework 6.1.1 model using system.data.sqlite 1.0.93
  24. Entity Framework/Linq EXpression converting from string to int
  25. “like” queries in Entity Framework
  26. Entity Framework Include() is not working
  27. How to pass parameters to the DbContext.Database.ExecuteSqlCommand method?
  28. Entity Framework Data Annotations Set StringLength VarChar
  29. EF 4.1 loading filtered child collections not working for many-to-many
  30. How to map Table per Type (TPT) inheritance in Entity designer?

Leave a Comment