KeyPress 和KeyDown,该怎么解决

KeyPress 和KeyDown
下面是一个combobox的keydown事件和一个keypress事件，我想问下，这代码到底是表达的什么意思 
 Private Sub cboDevId_KeyDown(ByVal eventSender As System.Object, ByVal eventArgs As System.Windows.Forms.KeyEventArgs) Handles cboDevId.KeyDown
        Dim KeyCode As Short = eventArgs.KeyCode
        Dim Shift As Short = eventArgs.KeyData \ &H10000
        Dim KeyAscii As New Object
        On Error GoTo cboDevId_KeyDownErr
        If KeyAscii <> 8 Then KeyAscii = 0
        Exit Sub

cboDevId_KeyDownErr:
        ShowErrorBox("frmGvApp13.cboDevId_KeyDown")
    End Sub

‘-------------------------------------------------
Private Sub cboDevId_KeyPress(ByVal eventSender As System.Object, ByVal eventArgs As System.Windows.Forms.KeyPressEventArgs) Handles cboDevId.KeyPress
        Dim KeyAscii As Short = Asc(eventArgs.KeyChar)
        On Error GoTo cboDevId_KeyPressErr

        'KeyAscii = 0
        If KeyAscii <> 8 Then KeyAscii = 0
        GoTo EventExitSub

cboDevId_KeyPressErr:
        ShowErrorBox("frmGvApp13.cboDevId_KeyPress")
EventExitSub:
        eventArgs.KeyChar = Chr(KeyAscii)
        If KeyAscii = 0 Then
            eventArgs.Handled = True
        End If
    End Sub
[解决办法]
屏蔽退格键之外的按键