复合控件开发中的一点心得

最新推荐文章于 2025-11-22 14:42:38 发布

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#datagrid #textbox #button #function #string #object

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博客介绍复合控件属性管理问题，当需暴露子控件众多属性时，若无分类管理会使属性浏览器混乱。作者在开发中把复合控件的子控件作为属性保存，给出了复合控件继承及Builder类、Designer类实现代码，还展示了复合控件属性及重载AddParsedSubObject方法的代码。

对于一个复合控件，其属性一般都是委托到子控件的属性。
但有时，我们需要将子控件的很多属性暴露出来。如果没有很好的分类管理，在属性浏览器里会很混乱。我在实际的开发过程中，是将子控件作为一个属性保存的。实现方法如下：
首先我的复合控件有一个datagrid，两个button，一个textbox。
复合控件(CompositeControl)继承于webcontrol,同时为其创建了builder类和designer类。
Builder类：
Public Overrides Function GetChildControlType(ByVal tagName As String, ByVal attribs As ystem.Collections.IDictionary) As System.Type
        If tagName.ToLower().EndsWith("textbox") Then
            Return GetType(TextBox)
        End If
        If tagName.ToLower().EndsWith("datagrid") Then
            Return GetType(DataGrid)
        End If
        If tagName.ToLower().EndsWith("button") Then
            Return GetType(Button)
        End If
        Return Nothing
End Function

Designer类：
Public Overrides Function GetPersistInnerHtml() As String
        Dim strWriter As StringWriter
        Dim htmlWriter As HtmlTextWriter
        Dim control As PressListBox

        strWriter = New StringWriter
        htmlWriter = New HtmlTextWriter(strWriter)
        control = CType(Me.Component, CompositeControl)
        MyBase.GetPersistInnerHtml()

        htmlWriter.Write(ControlPersister.PersistControl(control.TextBox))
        htmlWriter.Write(ControlPersister.PersistControl(control.DataGrid))
        htmlWriter.Write(ControlPersister.PersistControl(control.NextButton))
        htmlWriter.Write(ControlPersister.PersistControl(control.PreviousButton))
        Return strWriter.ToString
    End Function

复合控件属性：
<PersistenceMode(PersistenceMode.InnerProperty), NotifyParentProperty(True), _
        Description("Page Count"), Category("ChildControl")> _
        ReadOnly Property pageTextBox() As TextBox
        Get
            Me.EnsureChildControls()
            Return txtPageCount
        End Get
    End Property

    <PersistenceMode(PersistenceMode.InnerProperty), NotifyParentProperty(True), _
        Description("DisplayData"), Category("ChildControl")> _
        ReadOnly Property PageDataGrid() As NotifyDataGrid
        Get
            Me.EnsureChildControls()
            Return dgdList
        End Get
    End Property

    <PersistenceMode(PersistenceMode.InnerProperty), Category("ChildControl"), _
        Description("「＜」"), _
        NotifyParentProperty(True)> ReadOnly Property PreviousPageButton() As Button
        Get
            Me.EnsureChildControls()
            Return btnPrevious
        End Get
    End Property

<PersistenceMode(PersistenceMode.InnerProperty), Category("ChildControl"), _
        Description("「＞」"), _
        NotifyParentProperty(True)> ReadOnly Property NextPageButton() As Button
        Get
            Me.EnsureChildControls()
            Return btnNext
        End Get
    End Property

同时重载AddParsedSubObject方法：
Protected Overrides Sub AddParsedSubObject(ByVal obj As Object)
        Dim idName As Array
        If TypeOf (obj) Is TextBox Then
            Me.txtPageCount = obj
        End If

        If TypeOf (obj) Is DataGrid Then
            Me.dgdList = obj
        End If

        If TypeOf (obj) Is Button Then

            idName = Split(CType(obj, Button).ID.ToString, "_")

            If idName(1).ToString.Equals("NextPageButton") Then
                Me.btnNext = obj
            Else
                Me.btnPrevious = obj
            End If
        End If
    End Sub