求解释，跪求

Dim WithEvents adoPrimaryRS As Recordset
Dim mbChangedByCode As Boolean
Dim mvBookMark As Variant
Dim mbEditFlag As Boolean
Dim mbAddNewFlag As Boolean
Dim mbDataChanged As Boolean

Private Sub Form_Load()
  Dim db As Connection
  Set db = New Connection
  db.CursorLocation = adUseClient
  db.Open "PROVIDER=MSDASQL;dsn=通讯录;uid=;pwd=;"

  Set adoPrimaryRS = New Recordset
  adoPrimaryRS.Open "select 姓名,电话,qq from 通讯录", db, adOpenStatic, adLockOptimistic

  Dim oText As TextBox
  '绑定文本框到数据提供者
  For Each oText In Me.txtFields
    Set oText.DataSource = adoPrimaryRS
  Next

  mbDataChanged = False
End Sub

Private Sub Form_Resize()
  On Error Resume Next
  lblStatus.Width = Me.Width - 1500
  cmdNext.Left = lblStatus.Width + 700
  cmdLast.Left = cmdNext.Left + 340
End Sub

Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)
  If mbEditFlag Or mbAddNewFlag Then Exit Sub

  Select Case KeyCode
    Case vbKeyEscape
      cmdClose_Click
    Case vbKeyEnd
      cmdLast_Click
    Case vbKeyHome
      cmdFirst_Click
    Case vbKeyUp, vbKeyPageUp
      If Shift = vbCtrlMask Then
        cmdFirst_Click
      Else
        cmdPrevious_Click
      End If
    Case vbKeyDown, vbKeyPageDown
      If Shift = vbCtrlMask Then
        cmdLast_Click
      Else
        cmdNext_Click
      End If
  End Select
End Sub

Private Sub Form_Unload(Cancel As Integer)
  Screen.MousePointer = vbDefault
End Sub

Private Sub adoPrimaryRS_MoveComplete(ByVal adReason As ADODB.EventReasonEnum, ByVal pError As ADODB.Error, adStatus As ADODB.EventStatusEnum, ByVal pRecordset As ADODB.Recordset)
  '为这个 recordset 显示当前记录位置
  lblStatus.Caption = "Record: " & CStr(adoPrimaryRS.AbsolutePosition)
End Sub

Private Sub adoPrimaryRS_WillChangeRecord(ByVal adReason As ADODB.EventReasonEnum, ByVal cRecords As Long, adStatus As ADODB.EventStatusEnum, ByVal pRecordset As ADODB.Recordset)
  '验证代码置于此处
  '下列动作发生时该事件被调用
  Dim bCancel As Boolean

  Select Case adReason
  Case adRsnAddNew
  Case adRsnClose
  Case adRsnDelete
  Case adRsnFirstChange
  Case adRsnMove
  Case adRsnRequery
  Case adRsnResynch
  Case adRsnUndoAddNew
  Case adRsnUndoDelete
  Case adRsnUndoUpdate
  Case adRsnUpdate
  End Select

  If bCancel Then adStatus = adStatusCancel
End Sub

Private Sub cmdAdd_Click()
  On Error GoTo AddErr
  With adoPrimaryRS
    If Not (.BOF And .EOF) Then
      mvBookMark = .Bookmark
    End If
    .AddNew
    lblStatus.Caption = "添加记录"
    mbAddNewFlag = True
    SetButtons False
  End With

  Exit Sub
AddErr:
  MsgBox Err.Description
End Sub

Private Sub cmdDelete_Click()
  On Error GoTo DeleteErr
  With adoPrimaryRS
    .Delete
    .MoveNext
    If .EOF Then .MoveLast
  End With
  Exit Sub
DeleteErr:
  MsgBox Err.Description
End Sub

Private Sub cmdRefresh_Click()
  '只有多用户应用程序需要
  On Error GoTo RefreshErr
  adoPrimaryRS.Requery
  Exit Sub
RefreshErr:
  MsgBox Err.Description
End Sub

Private Sub cmdEdit_Click()
  On Error GoTo EditErr

  lblStatus.Caption = "编辑记录"
  mbEditFlag = True
  SetButtons False
  Exit Sub

EditErr:
  MsgBox Err.Description
End Sub
Private Sub cmdCancel_Click()
  On Error Resume Next

  SetButtons True
  mbEditFlag = False
  mbAddNewFlag = False
  adoPrimaryRS.CancelUpdate
  If mvBookMark > 0 Then
    adoPrimaryRS.Bookmark = mvBookMark
  Else
    adoPrimaryRS.MoveFirst
  End If
  mbDataChanged = False

End Sub

Private Sub cmdUpdate_Click()
  On Error GoTo UpdateErr

  adoPrimaryRS.UpdateBatch adAffectAll

  If mbAddNewFlag Then
    adoPrimaryRS.MoveLast              '移到新记录
  End If

  mbEditFlag = False
  mbAddNewFlag = False
  SetButtons True
  mbDataChanged = False

  Exit Sub
UpdateErr:
  MsgBox Err.Description
End Sub

Private Sub cmdClose_Click()
  Unload Me
End Sub

Private Sub cmdFirst_Click()
  On Error GoTo GoFirstError

  adoPrimaryRS.MoveFirst
  mbDataChanged = False

  Exit Sub

GoFirstError:
  MsgBox Err.Description
End Sub

Private Sub cmdLast_Click()
  On Error GoTo GoLastError

  adoPrimaryRS.MoveLast
  mbDataChanged = False

  Exit Sub

GoLastError:
  MsgBox Err.Description
End Sub

Private Sub cmdNext_Click()
  On Error GoTo GoNextError

  If Not adoPrimaryRS.EOF Then adoPrimaryRS.MoveNext
  If adoPrimaryRS.EOF And adoPrimaryRS.RecordCount > 0 Then
    Beep
     '已到最后返回
    adoPrimaryRS.MoveLast
  End If
  '显示当前记录
  mbDataChanged = False

  Exit Sub
GoNextError:
  MsgBox Err.Description
End Sub

Private Sub cmdPrevious_Click()
  On Error GoTo GoPrevError

  If Not adoPrimaryRS.BOF Then adoPrimaryRS.MovePrevious
  If adoPrimaryRS.BOF And adoPrimaryRS.RecordCount > 0 Then
    Beep
    '已到最后返回
    adoPrimaryRS.MoveFirst
  End If
  '显示当前记录
  mbDataChanged = False

  Exit Sub

GoPrevError:
  MsgBox Err.Description
End Sub

Private Sub SetButtons(bVal As Boolean)
  cmdAdd.Visible = bVal
  cmdEdit.Visible = bVal
  cmdUpdate.Visible = Not bVal
  cmdCancel.Visible = Not bVal
  cmdDelete.Visible = bVal
  cmdClose.Visible = bVal
  cmdRefresh.Visible = bVal
  cmdNext.Enabled = bVal
  cmdFirst.Enabled = bVal
  cmdLast.Enabled = bVal
  cmdPrevious.Enabled = bVal
End Sub

--------------------编程问答-------------------- --------------------编程问答-------------------- 一句都不懂啊你. --------------------编程问答-------------------- --------------------编程问答-------------------- 你不会要人家给你一句一句的解释吧?起码也要说哪句不懂吧？ --------------------编程问答--------------------

补充：VB ,  控件