【DevExpress】老版TreeList和GridControl 中控件 MouseWheel事件禁用解决方法

期望目标：TreeList和GridControl中禁用鼠标MouseWheel事件对控件值的更改。

处理思路：在TreeList_ShownEditor事件中，增加对ActiveEditor的MouseWheel事件处理，禁用掉即可。

遇到问题：老版DevExpress中对ActiveEditor.MouseWheel的Handle=true无效。

              参加官方问题地址 http://www.devexpress.com/Support/Center/Question/Details/Q148215

解决方法：

　　　　既然无法禁用值的改变，那就从改变后恢复着手。代码如下：

    Private activeEditor As DevExpress.XtraEditors.BaseEdit = Nothing       '当前编辑控件
    Private isMouseWheelChanged As Boolean = False                          '是否为鼠标滚轮滚动改变
    Private oActiveEditorOldValue As Object = Nothing                       '初始值

    Private Sub TreeList_ShownEditor(ByVal sender As System.Object, ByVal e As System.EventArgs)
        activeEditor = m_tree.ActiveEditor
        oActiveEditorOldValue = activeEditor.EditValue
        AddHandler activeEditor.MouseWheel, AddressOf ActiveEditor_MouseWheel
        AddHandler activeEditor.EditValueChanging, AddressOf ActiveEditor_EditValueChanging
    End Sub

    Private Sub TreeList_HiddenEditor(ByVal sender As Object, ByVal e As System.EventArgs)
        If activeEditor IsNot Nothing Then
            isMouseWheelChanged = False
            oActiveEditorOldValue = Nothing
        End If
    End Sub

    ’出自 http://caryliu.cnblogs.com
    Private Sub ActiveEditor_MouseWheel(ByVal sender As System.Object, ByVal e As MouseEventArgs)
        isMouseWheelChanged = True

        If oActiveEditorOldValue IsNot Nothing Then
            Try
                RemoveHandler activeEditor.EditValueChanging, AddressOf ActiveEditor_EditValueChanging
                activeEditor.EditValue = oActiveEditorOldValue
            Catch ex As Exception
            Finally
                AddHandler activeEditor.EditValueChanging, AddressOf ActiveEditor_EditValueChanging
            End Try
        End If

        '转化为列表滚动
        Dim scrollLines As Integer = SystemInformation.MouseWheelScrollLines
        If (scrollLines = -1) Then scrollLines = m_tree.ViewInfo.VisibleRowCount

        m_tree.TopVisibleNodeIndex += IIf(e.Delta > 0, -scrollLines, scrollLines)
    End Sub


    Private Sub ActiveEditor_EditValueChanging(ByVal sender As System.Object, ByVal e As DevExpress.XtraEditors.Controls.ChangingEventArgs)
        If isMouseWheelChanged Then
            e.Cancel = True
            Exit Sub
        End If

        oActiveEditorOldValue = e.OldValue
    End Sub