控件的属性在运行与设计模式切换时，属性值为丢失，可以要用WriteProperties来保存属性值，再用ReadProperties读取，具体情况如下：
1、在设计模式往运行模式切换时，先用WriteProperties保存属性值，由于在运行时要使用该值，所以用ReadProperties读出。
2、在结速运行状态切换到设计模式时，不需要保存控件在运行状态的值，所以不调用WriteProperties保存，而直接读取程序员在设计模式下的值。
3、WriteProperties及ReadProperties事件只在设计调试中有效，编译为EXE文件后不再有效。此两事件及PropBag对象只是为了方便设计而存在。
例程： '本控件是text与updown控件的结合，使用updown改变数据值 '也可手工改变text值 ' ' Dim m_UpMax As Long Dim m_DownMin As Long Dim m_value As Long Dim m_Enabled As Boolean
Private Sub Text1_Change() On Error GoTo Err Dim txti As Long
'txti用来零时保存text1值 txti = CLng(text1.Text) If txti > UpDown1.Max Then text1.Text = UpDown1.Max End If If txti < UpDown1.Min Then text1.Text = UpDown1.Min End If txti = CLng(text1.Text) UpDown1.value = txti Exit Sub
Err: text1.Text = UpDown1.value End Sub
Private Sub UpDown1_Change() text1.Text = UpDown1.value End Sub
Private Sub UserControl_Resize() On Error Resume Next Dim t As Long Dim b As Long t = UserControl.Width - UpDown1.Width b = UserControl.Height - 1 text1.Width = t text1.Height = b text1.Move 0, 0 UpDown1.Move t, 0 UpDown1.Height = b End Sub
Public Property Get UpMax() As Long UpMax = m_UpMax End Property
Public Property Let UpMax(ByVal vNewvalue As Long) m_UpMax = vNewvalue UpDown1.Max = m_UpMax PropertyChanged "UpMax" End Property
Public Property Get DownMin() As Long DownMin = m_DownMin End Property
Public Property Let DownMin(ByVal vNewvalue As Long) m_DownMin = vNewvalue UpDown1.Min = vNewvalue PropertyChanged "DownMin" End Property
Private Sub UserControl_WriteProperties(PropBag As PropertyBag) Call PropBag.WriteProperty("UpMax", m_UpMax, 0) Call PropBag.WriteProperty("DownMin", m_DownMin, 0) Call PropBag.WriteProperty("value", CLng(text1.Text), 0) Call PropBag.WriteProperty("Enabled", m_Enabled, True) End Sub
Private Sub UserControl_ReadProperties(PropBag As PropertyBag) '使用PropBag.ReadProperty时一定要有默认值，否则如果没有在设计时改变过属性值（ '即没有使用writeProperty保存属性值）就无法读取，会产生“运行时错误”
m_UpMax = PropBag.ReadProperty("UpMax", 0) m_DownMin = PropBag.ReadProperty("DownMin", 0) m_value = PropBag.ReadProperty("value", 0) m_Enabled = PropBag.ReadProperty("Enabled", True) UpDown1.Max = m_UpMax UpDown1.Min = m_DownMin UpDown1.value = m_value UpDown1.Enabled = m_Enabled text1.Text = m_value text1.Enabled = m_Enabled End Sub
Public Property Get value() As Long Attribute value.VB_UserMemId = 0 m_value = CLng(text1.Text) value = m_value End Property
Public Property Let value(ByVal vNewvalue As Long) If vNewvalue > m_UpMax Then m_value = m_UpMax ElseIf vNewvalue < m_DownMin Then m_value = m_DownMin Else m_value = vNewvalue End If text1.Text = m_value
PropertyChanged "value" End Property
Public Property
Get Enabled() As Boolean Enabled = m_Enabled End Property
Public Property Let Enabled(ByVal vNewvalue As Boolean) m_Enabled = vNewvalue UpDown1.Enabled = m_Enabled text1.Enabled = m_Enabled PropertyChanged "Enabled" End Property
转载于:https://www.cnblogs.com/feima-lxl/archive/2008/05/03/1180553.html
相关资源：数据结构—成绩单生成器