Showing classes to user and instantiating selected type - vb.net

Question

I'm starting to learn about Reflection in VB.NET, and I have a little example problem I'm working on to understand some concepts.
So I have one interface implemented by three classes:
Public Interface IVehicle
Sub SayType()
End Interface
Public Class Bike
Implements IVehicle
Public Sub SayType() Implements IVehicle.SayType
MsgBox("I'm a bike")
End Sub
End Class
Public Class Car
Implements IVehicle
Public Sub SayType() Implements IVehicle.SayType
MsgBox("I'm a car")
End Sub
End Class
Public Class Plane
Implements IVehicle
Public Sub SayType() Implements IVehicle.SayType
MsgBox("I'm a plane")
End Sub
End Class
I would like the user to select one type of vehicle of all the vehicles available, instantiate one object of this type and call its method "SayType".
So, with this situation, I have 2 questions
The 1st one: I have thought about filling one ComboBox control with all the classes which implement the interface IVehicle. I have searched how to do so with reflection, and I've came up with this solution:
Private Function ObtainVehicleTypes() As IEnumerable(Of Type)
Dim types As IEnumerable(Of Type) = _
Reflection.Assembly.GetExecutingAssembly.GetTypes.Where(Function(t) _
t.GetInterface("IVehicle") IsNot Nothing)
Return types
End Function
With those types, I fill the ComboBox like this, which also works fine:
Private Sub AddTypesOfVehicles()
Dim types As IEnumerable(Of Type) = ObtainVehicleTypes()
For Each t As Type In types
ComboBox1.Items.Add(t.Name)
Next
End Sub
The problem is that, when I try to retrieve the item selected by the user and obtain the type asociated like shown below, I get Nothing, since the String doesn't contain the AssemblyName, only the Class name:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim type As Type = TryCast(ComboBox1.SelectedItem, Type) 'Here I get Nothing
Dim v As IVehicle = TryCast(Activator.CreateInstance(type), IVehicle)
v.SayType()
End Sub
I have also tried to to add this to the combobox:
For Each t As Type In types
ComboBox1.Items.Add(t) 'Adding the type, not only its name.
Next
But then it displays the AssemblyName to the user, which I want to avoid.
So, the question is... how would you do to show the classes to the user and the retrieve them correctly to instantiate an object of the chosen class?
The 2nd question: Do you consider this as a good approach? Would you suggest something simpler?
Thanks!

Answer 1

I do not understand the need of the method SayType on the interface. All types implements the GetType method which will return the info you'll need.
Dim vehicles As IVehicle() = New IVehicle() {New Bike(), New Car(), New Plane()}
For Each vehicle As IVehicle In vehicles
MsgBox(String.Format("I'm a {0}", vehicle.GetType().Name.ToLower()))
Next
'This will produce:
'------------------
'I'm a bike
'I'm a car
'I'm a plane
'------------------
This is how you could populate the combobox:
Dim t = GetType(IVehicle)
Dim list As List(Of Type) = Assembly.GetExecutingAssembly().GetTypes().Where(Function(x As Type) ((x <> t) AndAlso t.IsAssignableFrom(x))).ToList()
Me.ComboBox1.DataSource = list
Me.ComboBox1.DisplayMember = "Name"
And to retrieve the type:
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles saveButton.Click
If (Me.ComboBox1.SelectedIndex <> -1) Then
Dim t As Type = TryCast(Me.ComboBox1.SelectedItem, Type)
If (Not t Is Nothing) Then
MsgBox(t.FullName)
End If
End If
End Sub
Edit
A more real-world example of an IVehicle interface would be something like:
Public Interface IVehicle
ReadOnly Property Manufacturer() As String
ReadOnly Property Model() As String
Property Price() As Decimal
End Interface

Answer 2

combobx problem its Excellent answered by #Bjørn-Roger Kringsjå.
Here are additional improvements:
ObtainVehicleTypes:
Private Function ObtainVehicleTypes() As IEnumerable(Of Type)
Dim IVehicleType = GetType(IVehicle)
Dim types As IEnumerable(Of Type) = _
Reflection.Assembly.GetExecutingAssembly.GetTypes.Where(
Function(t) IVehicleType.IsAssignableFrom(t) AndAlso t.IsClass = True)
Return types
End Function
Private Sub AddTypesOfVehicles()
Dim types As IEnumerable(Of Type) = ObtainVehicleTypes().ToArray()
ComboBox1.DisplayMember = "Name"
ComboBox1.DataSource = types
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim type As Type = TryCast(ComboBox1.SelectedItem, Type)
Dim v As IVehicle = TryCast(Activator.CreateInstance(type), IVehicle)
v.SayType()
End Sub