Question

Possible Duplicate:
LEFT OUTER JOIN in LINQ

How to make LINQ query with left outer joins?

Answer 1

You can use Enumerable.DefaultIfEmpty Method for left outer join.

You may see: How to: Perform Left Outer Joins (C# Programming Guide) – MSDN

Consider the following example from MSDN,

class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

class Pet
{
    public string Name { get; set; }
    public Person Owner { get; set; }
}

Left outer join query can be:

var query = from person in people
            join pet in pets on person equals pet.Owner into gj
            from subpet in gj.DefaultIfEmpty()
            select new { person.FirstName, PetName = (subpet == null ? String.Empty : subpet.Name) };