This converts a vertical list to a comma-delimited list with each entry enclosed in double quotes.
With a vertical list in a textbox, just select the lines to convert and call the code from a toolstrip button. Conversion is very fast. It ignores blank lines within the list, but will tack on an extra comma if you select a blank line below the last list entry.
Private Sub ToolStripButton3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ToolStripButton3.Click
myStr = String.Empty
Dim arr() As String = txt.SelectedText.Split(Chr(10))
For l = 0 To arr.Length - 1
If arr(l).Length > 0 Then
myStr &= Chr(34) & arr(l) & Chr(34)
If l < arr.Length - 1 AndAlso arr(l).Length > 0 Then
myStr &= ","
End If
End If
Next
txt.SelectedText = myStr
End Sub