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LINQ Examples

In order to learn like, take a look a the LINQ-resources and tutorials out on the Internet. For example the LINQ-Overview at MSDN or at this example-collection. Here are a few db4o LINQ examples.

Simplest Possible Query

This query just returns all persons.

var allPersons = from Person p in container
                 select p;
LinqExamples.cs: Simple query
Dim allPersons = From p In container _
 Select p
LinqExamples.vb: Simple query

Query For a Name

This query searches for a person by name.

var allPersons = from Person p in container
                 where p.Name.Equals("Joe")
                 select p;
LinqExamples.cs: Query for name
Dim allPersons = From p As Person In container _
 Where p.Name.Equals("Joe") _
 Select p
LinqExamples.vb: Query for name

Query For a Certain Age

This queries for a certain age.

var allPersons = from Person p in container
                 where p.Age > 21
                 select p;
LinqExamples.cs: Query with a constraint
Dim allPersons = From p As Person In container _
 Where p.Age > 21 _
 Select p
LinqExamples.vb: Query with a constraint

Sorting The Result Of A Query

Sort the results of a query.

var allPersons = from Person p in container
                 where p.Age > 21
                 orderby p.Name
                 select p;
LinqExamples.cs: Use sorting on the query
Dim allPersons = From p As Person In container _
 Where p.Age > 21 _
 Order By p.Name _
 Select p
LinqExamples.vb: Use sorting on the query

Get The IQueryable Interface

You can get the .NET IQueryable interface for db4o

IQueryable<Person> personQuerable = container.AsQueryable<Person>();
var adults = from p in personQuerable
             where p.Age > 18
             orderby p.Name
             select p;
LinqExamples.cs: Get a IQueryable-instance
Dim personQuerable As IQueryable(Of Person) = container.AsQueryable(Of Person)()
Dim adults = From p In personQuerable _
 Where p.Age > 18 _
 Order By p.Name _
 Select p
LinqExamples.vb: Get a IQueryable-instance