【转】自制控件的属性保存(WriteProperties、ReadProperties)

本文转自：http://www.hbjjrb.com/Jishu/vb/200704/9980.html

一年前，VB中在编制OCX控件时的一点心得，发出来一起共享。
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