Editing the contents of a ListBox

Question

I have a ListBox with various rows of data (items that someone is buying, basically), and when the user clicks on a row it populates a textbox on the side with the quantity of how many of that thing he's buying. For example, one row might be "Pencils, $5, 3" and clicking the row makes "3" appear in the textbox.

If the user changes that 3 to a 7, for example, I want that to be put back into the row, so we now have "Pencils, $5, 7"

How do I do that?

Answer 1

You need to program the Listbox's SelectedIndexChanged event and the Textbox's TextChanged event. Here's your snippet:

Private Sub ListBox1_SelectedIndexChanged( _
    ByVal sender As System.Object, ByVal e As System.EventArgs) _
    Handles ListBox1.SelectedIndexChanged

    // Exit if no item is selected
    If ListBox1.SelectedItem Is Nothing Then Exit Sub

    // Get the item's text
    Dim item As String = ListBox1.SelectedItem.ToString

    // Keep only the last part
    item = item.Substring(item.LastIndexOf(", ") + 2)

    // Update the textbox
    TextBox1.Text = item

End Sub

Private Sub TextBox1_TextChanged( _
    ByVal sender As System.Object, ByVal e As System.EventArgs) _
    Handles TextBox1.TextChanged

    // Exit if no item is selected
    If ListBox1.SelectedItem Is Nothing Then Exit Sub

    // Get the item's text, removing the last part
    Dim item As String = ListBox1.SelectedItem.ToString
    item = item.Substring(0, item.LastIndexOf(", ") + 2)

    // Add the numerical value of the textbox's text
    item &= Val(TextBox1.Text)

    // Get the index of the selected item
    Dim index As Integer = ListBox1.SelectedIndex

    // Remove the old item, add the new one and select it
    ListBox1.Items.RemoveAt(index)
    ListBox1.Items.Insert(index, item)
    ListBox1.SelectedIndex = index

End Sub