How can I update in Linq an entity that is disconnected from database?

Question

Code below does not run correctly and throws InvalidOperationExcepiton.

public void Foo()
{
 DataContext context = new DataContext();
 LinqEntity item = new LinqEntity(){ Id = 1, Name = "John", Surname = "Doe"} ;
 context.LinqEntities.Attach(item, true);
}

Answer 1

By default, the entities will use all fields for checking concurrency when making edits. That's what's throwing the InvalidOperationException.

This can be setting the Update Check property for all fields to Never. This must be done on all fields to attach the entity as modified. If this is done, an additional call to context.SubmitChanges() will save the data.

Alternatively, if you know the original values, you can attach and then make the updates, but all values that are being checked must match the original values.

LinqEntity item = new LinqEntity(){ Id = 1, Name = "OldName", Surname = "OldSurname"}; 
context.LinqEntities.Attach(item);
item.Name = "John";
item.Surname = "Doe";
context.SubmitChanges();