Is it possible to use SelectMany() and have it behave like a left join?
I am trying to flatten an Entity Object into a tabular format so I can use it as a data source for an .rdlc report. The SelectMany() works like a charm so long as there is a child object, but I want to see all of the parent objects regardless of whether it has children or not.
public class Owner
{
public int ownerID { get; set; }
public string ownerName { get; set; }
public List<Pet> pets { get; set; }
}
public class Pet
{
public int petID { get; set; }
public string petName { get; set; }
public string petType { get; set; }
}
public void GetOwners()
{
List<Owner> owners = new List<Owner>();
owners.Add(new Owner{ownerID=1, ownerName="Bobby", pets = null});
owners.Add(new Owner
{
ownerID = 2,
ownerName = "Ricky",
pets = new List<Pet>(){
new Pet{petID=1, petName="Smudge", petType="Cat"},
new Pet{petID=2, petName="Spot", petType="Dog"}}
});
var ownersAndPets = owners.SelectMany(o => o.pets
.Select(p => new { o.ownerName, p.petName }));
}
This will make ownersAndPets look like:
ownerName = "Ricky", petName = "Smudge"
ownerName = "Ricky", petName = "Spot"
What I need is:
ownerName = "Bobby", petName = null
ownerName = "Ricky", petName = "Smudge"
ownerName = "Ricky", petName = "Spot"
Make sure the dataset is enumerable and then use "DefaultIfEmpty".
var ownersAndPets = owners
.SelectMany(o => o.pets
.DefaultIfEmpty()
.Select(p => new
{
o.ownerName,
p.petName
}));
NOTE: I didn't test this particular piece of code, but I have used this before so I know the it can be done.
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