How to make a default item for ComboBox with a DataSource - vb.net

Question

In my application I have a data bound ComboBox that looks like this:
Dim listaCategoria As List(Of Ccategoria) = CAD.ObterTodosC()
cbxAlterarCg.DataSource = listaCategoria
cbxAlterarCg.DisplayMember = "nomeCategoria"
cbxAlterarCg.ValueMember = "idCategoria"
The class code (CAD):
Public Shared Function ObterTodosC() As List(Of Ccategoria)
Dim lstTodos As List(Of Ccategoria) = New List(Of Ccategoria)
Try
Using con As SqlConnection = New SqlConnection()
con.ConnectionString = myDAC._connectionString
Using cmd As SqlCommand = con.CreateCommand()
cmd.CommandText = "select * from Categoria"
con.Open()
Dim dr As SqlDataReader = cmd.ExecuteReader()
While dr.Read()
Dim p As Ccategoria = New Ccategoria()
p.IdCategoria = dr.GetInt32(0)
p.NomeCategoria = dr.GetString(1)
lstTodos.Add(p)
End While
End Using
End Using
Catch ex As SqlException
Throw ex
Catch ex As Exception
Throw ex
End Try
Return lstTodos
End Function
And the attributes:
Public Class Ccategoria
Private _idCategoria As Integer
Private _nomeCategoria As String
(...)
My ComboBox displays "nomeCategoria" with the "idCategoria" value right.
Now my question, like the title says can I create a default read only item so saying ("select your category") or something like that?
I've seen some other tutorials but none of them with ComboBox which are data bounded.

Answer 1

What you could do is add a Ccategoria() to lstTodos just under Dim lstTodos As List(Of Ccategoria) = New List(Of Ccategoria) like so:
Public Shared Function ObterTodosC() As List(Of Ccategoria)
Dim lstTodos As List(Of Ccategoria) = New List(Of Ccategoria)
Dim p As Ccategoria = New Ccategoria()
p.IdCategoria = 0
p.NomeCategoria = "select your category"
lstTodos.Add(p)
Try
Using con As SqlConnection = New SqlConnection()
con.ConnectionString = myDAC._connectionString
Using cmd As SqlCommand = con.CreateCommand()
cmd.CommandText = "select * from Categoria"
con.Open()
Dim dr As SqlDataReader = cmd.ExecuteReader()
While dr.Read()
Dim p As Ccategoria = New Ccategoria()
p.IdCategoria = dr.GetInt32(0)
p.NomeCategoria = dr.GetString(1)
lstTodos.Add(p)
End While
End Using
End Using
Catch ex As SqlException
Throw ex
Catch ex As Exception
Throw ex
End Try
Return lstTodos
End Function
In doing this you are simply adding to the DataSource. You could then look into providing validation by checking to see if idCategoria is 0. If it is you may want to consider showing a MessageBox to the user prompting them to pick a category.