Question

I’m trying to order a list by enum please see below:

Public Class AnimalsToProcess
Implements ICloneable

       Enum AnimalOrder
        Dog
        Cat
        Horse
        Fish
       End Enum


    Public Property _animalList As List(Of Animal)

    Public Sub New()

    End Sub

    Function Clone() As AnimalsToProcess

    End Function

    Private Function ICloneable_Clone() As Object Implements ICloneable.Clone
        Return Clone()
    End Function

    Public Sub Add(animalToAdd As Animal)
        _animalList.Add(animalToAdd)
    End Sub

    Public Sub GetAnimals() as list(of Animal)
        _animalList() 'this should be an ordered BY AnimalOrder Enum
    End Sub
End Class

The Add method is called by the external code by passing a value , eg:

animals.add(Fish)  
animals.add(Horse)  
animals.add(Cat)`

but when the GetAnimals is called it should return a list ordered by theEnum AnimalOrder.

hence then list should contain the follwing animals in this order cat,horse,fish

thank you.

Answer 1

Enums use integers internally for each value. If you don’t set them explicitly, they’re auto-assigned in the order defined in the enum, starting with 0.

You should be able to cast your String value to your enum and from there to an integer. Something like (untested)..

Public Function GetAnimals() as list(of Animal)
    Return _animalList.OrderBy(function(x) Cint(DirectCast(Enum.Parse(GetType(AnimalOrder), x), AnimalOrder)))
End Sub

Note that you’re referring to the value as type Animal but don’t have a definition of that in your Q. If you need to access a property to get the value to match to the Enum, say AnimalTypeString…

Public Function GetAnimals() as list(of Animal)
    Return _animalList.OrderBy(function(x) Cint(DirectCast(Enum.Parse(GetType(AnimalOrder), x.AnimalTypeString), AnimalOrder)))
End Sub

OR If the AnimalType property on your animal points directly at the enum value (Which would be sensible) you can skip out the conversion to enum…

Public Function GetAnimals() as list(of Animal)
    Return _animalList.OrderBy(function(x) Cint(X.AnimalType))
End Sub