Beginning ASP.NET 4.5 in CSharp and VB Opsylum

508 x CHAPTER 14 LINQ AND THE ADO.NET ENTITY FRAMEWORK
Select
The Select keyword (select in C#) is used to retrieve objects from the source you are querying. In
this example you see how to select an object of an existing type. Later in this chapter you see how to
define new object shapes on the fly.
VB.NET
Dim allReviews = From r In myEntities.Reviews
Select r
C#
var allReviews = from r in myEntities.Reviews
select r;
The r variable in this example is referred to as a range variable that is only available within the current
query. You typically introduce the range variable in the From clause, and then use it again in the
Where and Select clauses to filter the data, and to indicate the data you want to select. Although
you can choose any name you like, you often see single-letter variables like the r (for Review) or
you see the singular form of the collection you are querying (review instead of r in the preceding
examples).
From
Although not considered a standard query operator — because it doesn’t operate on the data but
rather points to the data — the From clause (from in C#) is an important element in a LINQ query,
because it defines the collection or data source that the query must act upon. In the previous example,
the From clause indicates that the query must be executed against the Reviews collection that is
exposed by the myEntities object in EF.
Order By
With Order By (orderby in C#, without the space that VB.NET uses) you can sort the items in
the result collection. Order By is followed by an optional Ascending or Descending (ascending
and descending in C#) keyword to specify sort order. You can specify multiple criteria by separating
them with a comma. The following query returns a list of genres, first sorted by SortOrder in
descending order, then sorted on their Name in ascending order (the default):
VB.NET
Dim allGenres = From g In myEntities.Genres
Order By g.SortOrder Descending, g.Name
Select g
C#
var allGenres = from g in myEntities.Genres
orderby g.SortOrder descending, g.Name
select g;