我试图将报价项数据格式化为JSON对象，以便稍后保存到MySQL。下面的代码生成JSONObject，它返回一个空JSON对象，如下所示：[{}]，即使Quote_Items_Info_Data不为空。未触发任何错误！为什么JsonConvert没有序列化？

Friend Class JSON_Quote_Item
    Friend Property ItemNumber As String
    Friend Property ItemDescription As String
    Friend Property ItemQty As String
    Friend Property ItemPrice As String
    Public Sub New()
    End Sub
    Public Sub New(ByVal _ItemNumber As String, ByVal _ItemDescription As String, ByVal _itemQty As String, ByVal _itemPrice As String)
        ItemNumber = _ItemNumber.Trim.Replace(vbCrLf, "\r\n").Replace(Chr(34), "\" & Chr(34)).Replace("'", "\'")
        ItemDescription = _ItemDescription.Trim.Replace(vbCrLf, "\r\n").Replace(Chr(34), "\" & Chr(34)).Replace("'", "\'")
        ItemQty = _itemQty.Trim
        ItemPrice = _itemPrice.Trim
    End Sub
End Class
'
'
''' <summary>
''' Convert all Quote items to a JSON object on the form and save it to the server DB.
''' senderFRM is the Quote Creator/Editor. Following an example from: https://www.newtonsoft.com/json/help/html/SerializingCollections.htm
''' and https://www.newtonsoft.com/json
''' </summary>
''' <param name="senderFRM"></param>
''' <returns></returns>
Friend Function SaveAllQuoteItems(senderFRM As frmQuotesCreatorEditor) As Boolean
    Try
        'make sure I will not run into an exception!
        If senderFRM IsNot Nothing AndAlso String.IsNullOrEmpty(senderFRM.txtQuoteNumber.Text.Trim) = False Then
            Dim QuoteNumber As String = senderFRM.txtQuoteNumber.Text.Trim
            'Holds a list of the custom class JSON_Quote_Item as T and contain all the form quote items data.
            Dim Quote_Items_Info_Data As List(Of JSON_Quote_Item) = New List(Of JSON_Quote_Item)
            '

            '
            'Go thru all FlowLayout controls in the form with the finality of finding the Quote items data and put this into a JSON (serialized) string.
            For Each myPanel As Panel In senderFRM.flpQuoteItems.Controls.OfType(Of Panel)
                Dim myElementHost As ElementHost = myPanel.Controls.OfType(Of ElementHost).FirstOrDefault
                Dim MyUserControl_QuoteItem As UserControl_QuoteItem = TryCast(myElementHost.Child, UserControl_QuoteItem)
                '
                Dim myQuoteItemNumber As String = MyUserControl_QuoteItem.txtItemNumber.Text
                Dim myQuoteItemDescription As String = MyUserControl_QuoteItem.txtItemDescription.Text
                Dim myQuoteItemQty As String = MyUserControl_QuoteItem.txtItemQty.Text
                Dim MyQuoteItemPrice As String = MyUserControl_QuoteItem.txtItemListedCustomerPrice.Text
                '
                'Perhaps not necessary but here to check that all parameters contain data.
                If String.IsNullOrEmpty(myQuoteItemNumber) = False And String.IsNullOrEmpty(myQuoteItemDescription) = False And
                    String.IsNullOrEmpty(myQuoteItemQty) = False And String.IsNullOrEmpty(MyQuoteItemPrice) = False Then
                    'add the data to the list of UserControl_QuoteItem
                    Quote_Items_Info_Data.Add(New JSON_Quote_Item(myQuoteItemNumber, myQuoteItemDescription, MyQuoteItemPrice, myQuoteItemQty))
                End If
            Next
            '
            Dim JSONObject As Object = DBNull.Value
            If Quote_Items_Info_Data IsNot Nothing AndAlso Quote_Items_Info_Data.Count > 0 Then
                '
                'NuGet - Newtonsoft.Json.JsonConvert
                'Return as string, but will keep as an object to be able to use it on the parameterization of the SQL query later!
                JSONObject = JsonConvert.SerializeObject(Quote_Items_Info_Data)
            End If
            '
            Console.WriteLine(JSONObject.ToString)
            'JSONObject is returning an empty JSON Object returning this: [{}] ,  even though Quote_Items_Info_Data was not empty.
            'Why on earth is JsonConvert is not serializing?
            '
            'Code to save to the quote column in the database code goes here if the above ever Works!
        End If
        Return True
    Catch ex As Exception
        Console.WriteLine(ex.Message)
    End Try
    Return False
End Function