Fill TextBox from ListBox on click

Question

I have a form in a WinForms application that has a Textbox called txtSupplier, a button called btnSrchSuppliers, a label called lblSuppName, and a ListBox lstSuppliers.

When the user clicks the button, it goes to a database and fetches a list of suppliers and lists them in the ListBox, selecting a supplier from the list fills the Textbox with his ID and the label with the name.

This code is used and fully working but I feel that it is not quite good.

Private Sub btnSrchSuppliers_Click(sender As Object, e As EventArgs) Handles btnSrchSuppliers.Click
        Dim suppliers As New List(Of SupplierDTO)

        lblSuppName.Text = String.Empty

        If lstSuppliers.Visible Then
            lstSuppliers.Hide()

        Else
            Try
                lstSuppliers.ValueMember = "ID"
                lstSuppliers.DisplayMember = "Description"
                lstSuppliers.BringToFront()
                suppliers = ItemBAL.SelectSuppliers(txtSupplier.Text.Trim())    'Get Suppliers

                If suppliers.Count = 0 Then
                    MsgBox("Supplier not found", MsgBoxStyle.Critical, "Supplier")
                ElseIf suppliers.Count >= 1 Then
                    lstSuppliers.DataSource = suppliers

                    If suppliers.Count > 1 Then
                        lstSuppliers.Visible = True
                    Else
                        lstSuppliers.SelectedIndex = 0
                        lstSuppliers_Click(lstSuppliers, e)
                    End If
                End If
            Catch ex As Odbc.OdbcException
                MsgBox(ex.Message, MsgBoxStyle.Critical, "sql error")
            Catch ex As Exception
                MsgBox(ex.Message, MsgBoxStyle.Critical, "general error")
            End Try
        End If
    End Sub

and

Private Sub lstSuppliers_Click(lstSuppliers As ListBox, e As EventArgs) Handles lstSuppliers.Click
        Dim selectedSupp As SMS.DTO.SupplierDTO

        selectedSupp = lstSuppliers.SelectedItem
        lstSuppliers.Visible = False
        txtSupplier.Text = selectedSupp.ID
        lblSuppName.Text = selectedSupp.Description
    End Sub

What can be improved?

Answer 1

As I understand your description, the form loads without data. The user initiates the data loading by clicking a button and then they select the desired supplier. To me, that is asking the user to do too much.

I prefer front-loading the data. Somewhere during program initialization, make your database call using an async method. Maybe something as:

Dim suppliers As New List()
supplier = Await GetSuppliersAsync()

Async Function GetSuppliersAsync()
    Return Task.Run(Function() SupplierDTO().GetList())
End Function

Then as the form loads you can populate the list box with the results from the suppliers object and eliminate one step the user has to perform.

This is how I would approach it. I am open to community scrutiny on this approach.

Edit to answer

Let's say you load a data structure with a list of suppliers on application, or form, init. In that case, the entire btnSrchSuppliers_Click subroutine is obsolete. You can remove it which will clean up the code smell.