Private Sub Form1_Paint(ByVal sender As Object, ByVal e As _
  System.Windows.Forms.PaintEventArgs) Handles MyBase.Paint
        Dim p As New System.Drawing.Pen(System.Drawing.Color.Red, 2)
        Dim r As System.Drawing.Rectangle
        For Each c As System.windows.Forms.Control In Me.Controls
            If TypeOf c Is System.Windows.Forms.TextBox Then
                r = New System.Drawing.Rectangle(c.Location, c.Size)
                e.Graphics.DrawRectangle(p, r)
            End If
        Next
End Sub