CODEWITHSUNDEEP
vb.netclasscollectionscombobox
Martin Matus Jr
Martin Matus Jr

Reputation: 31

Add items from a collection to a combo box

I have a class that reads from a text file, and adds it to a collection. I'm trying to figure out how to read from the collection to populate a combobox upon loading of the program.

BillingData Class

Public ReadOnly Property Clients As Collection
    Get
        Return mClients
    End Get
End Property

Sub New()


    mClientFile = OpenText("clients.txt")

    Dim mClients As New Collection

    While Not mClientFile.EndOfStream
        mClients.Add(mClientFile.ReadLine())
    End While


    mClientFile.Close()

mainForm

Private Sub frmMain_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    client = New BillingData()

    Dim i As Integer
    While i < client.Clients.Count
        cbClient.Items.AddRange(client.Clients(i))
        i = i + 1
    End While
End Sub

Upvotes: 1

Views: 6390

Answers (2)

Mash
Mash

Reputation: 1536

I made 3 changes to the frmMain_Load subroutine.

  1. Initialized counter i to 1.
  2. Changed the while loop condition to <=.

  3. Used Add instead of AddRange.

    Private Sub frmMain_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    client = New BillingData()

    Dim i As Integer = 1
    While i <= client.Clients.Count
        cbClient.Items.Add(client.Clients(i))
        i = i + 1
    End While

End Sub

An interesting thing to note for the first change (initializing i to 1): The value of Clients at index 0 is "empty placeholder for a 1-based array". This basically means the collection starts at index 1. The code will sort of throw a phantom exception that never gets caught - this is typical in VB.net form load routines. You can test this out by setting a breakpoint in your load code and see that it never gets to the line i = i + 1. If you placed your code in a button click event instead, you would see the code break on the exception. Moral of the story is to be careful on any code that you put on form load routines, because you do not always get immediate feedback if there is a bug in the code.

Upvotes: 2

Mark Hall
Mark Hall

Reputation: 54532

You can try adding your Collection to the ComboBox's DataSource. If your problem is that your Collection is not initialized before you add it to the ComboBox you can add an event to your BillingData Class that is raised when the data is ready. You could then add the collection to your ComboBox in the Event Handler.

cbClient.DataSource = client.Clients

Upvotes: 1

Related Questions