添加如下属性，问题解决.

Added following attributes and the problem is solved.

    <EditorBrowsable(EditorBrowsableState.Always)> _
    <Browsable(True)> _
    <DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)> _
    <Bindable(True)> _
    Public Overrides Property Text() As String
        Get
            Return lblText.Text
        End Get
        Set(ByVal value As String)
            lblText.Text = value
        End Set
    End Property