VB.NET System.ComponentModel.Component.Site tag cannot be serialized, because it's an interface

Question

Imports System.IO.Ports
Imports System.Data.SqlClient
Imports System.Collections.ObjectModel
Imports System.Data.Common
Imports Microsoft
Imports System.Data.SqlTypes
Imports System.Xml
Imports System.Collections.Specialized.BitVector32
Imports System.Security.Cryptography.X509Certificates
Imports System.Xml.Serialization
Imports System.Windows.Forms.AxHost

Public Class sqlConnector
    'Private Session
    Private pSqlServer, pSqlUsername, pSqlPassword, pSqlDatabase, pSqlTable As String
    Private pSqlConnection As New SqlConnection
    Private pSqlCmd As SqlCommand
    Private pSqlReader As SqlDataReader

    'Public Session
    Public Sub New()

    End Sub
    Public Property serverName As String
        Get
            Return pSqlServer
        End Get
        Set(value As String)
            pSqlServer = value
        End Set
    End Property
    Public Property userName As String
        Get
            Return pSqlUsername
        End Get
        Set(value As String)
            pSqlUsername = value
        End Set
    End Property
    Public Property dataBaseName As String
        Get
            Return pSqlDatabase
        End Get
        Set(value As String)
            pSqlDatabase = value
        End Set
    End Property
    Public Property password As String
        Get
            Return pSqlPassword
        End Get
        Set(value As String)
            pSqlPassword = value
        End Set
    End Property
    Public Property table As String
        Get
            Return pSqlTable
        End Get
        Set(value As String)
            pSqlTable = value
        End Set
    End Property
    Public Function connect()
        Try
            pSqlConnection = New SqlConnection("Server=" & pSqlServer & ";User Id=" & pSqlUsername & ";Password=" & pSqlPassword)
            pSqlConnection.Open()
            Return 0
        Catch ex As Exception
            MsgBox("Error: " & ex.Message, vbCritical + vbOKOnly)
            Return -1
        End Try
    End Function
    Public Function send(command As String)
        If pSqlConnection.State <> ConnectionState.Open Then
            If connect() <> 0 Then Exit Function
        End If
        Try
            pSqlCmd = pSqlConnection.CreateCommand
            pSqlCmd.CommandText = command
            pSqlReader = pSqlCmd.ExecuteReader()
            If pSqlReader.HasRows Then
                Return pSqlReader
            Else
                Return 0
            End If
        Catch ex As Exception
            MsgBox("Error: " & ex.Message, vbCritical + vbOKOnly)
            Return -1
        End Try
    End Function
    Public Sub disConnect()
        pSqlConnection.Close()
    End Sub
    Protected Overrides Sub Finalize()
        disConnect()
    End Sub

End Class
Public Class Scale
    'Private Session
    Public pScaleName As String
    Private pScaleId As Integer
    Private pSerialConnection As SerialPort
    Private pSqlConnection As sqlConnector
    Private Sub SendToSQL(data As String)
        Dim splittedData() As String = data.Split(" ")
        pSqlConnection.send("USE" & pSqlConnection.dataBaseName & "; UPDATE " & pSqlConnection.table & " set value=" & splittedData(0) & ", unit=" & splittedData(1) & " where deviceid=" & pScaleId)
    End Sub
    Private Sub DataReceivedHandler(sender As Object, e As SerialDataReceivedEventArgs)
        Dim buffered As String = ""
        Try
            Dim rcv As String = pSerialConnection.ReadLine()

            buffered = rcv.Trim()
            If buffered <> "" Then
                SendToSQL(buffered)
            End If
        Catch ex As Exception
        End Try
    End Sub
    Private Sub serialDisConnect()
        pSerialConnection.Close()
    End Sub

    'Public Session
    Public Sub New()

    End Sub
    Public Property sqlConnection As sqlConnector
        Get
            Return pSqlConnection
        End Get
        Set(value As sqlConnector)
            pSqlConnection = value
        End Set
    End Property
    Public Property serialConnection As SerialPort
        Get
            Return pSerialConnection
        End Get
        Set(value As SerialPort)
            pSerialConnection = value
        End Set
    End Property
    Public Property name As String
        Get
            Return pScaleName
        End Get
        Set(value As String)
            pScaleName = value
        End Set
    End Property
    Public Property id As Integer
        Get
            Return pScaleId
        End Get
        Set(value As Integer)
            pScaleId = value
        End Set
    End Property
    Public Function serialConnect()
        Try
            pSerialConnection.Open()
            AddHandler pSerialConnection.DataReceived, AddressOf DataReceivedHandler
            Return 0
        Catch ex As Exception
            MsgBox("Error opening port " & CStr(pSerialConnection.PortName) & "! Error: " & ex.Message, "Error opening port", vbCritical + vbOKOnly)
            Return -1
        End Try
    End Function
    Protected Overrides Sub Finalize()
        serialDisConnect()
    End Sub
End Class

Public Class Settings
    Private pFileName As String
    Private pSections As New List(Of Section)

    <System.Xml.Serialization.XmlInclude(GetType(Scale))>
    <System.Xml.Serialization.XmlInclude(GetType(sqlConnector))>
    Public Class Section
        Private pName As String
        Private pContent As New List(Of Object)
        Public Property name As String
            Get
                Return pName
            End Get
            Set(value As String)
                pName = value
            End Set
        End Property
        Public ReadOnly Property content(item As String) As Object
            Get
                For i As Integer = 0 To pContent.Count() - 1
                    If pContent(i).name = item Then Return pContent(i)
                Next
                Return Nothing
            End Get
        End Property
        Public Sub addContent(item)
            pContent.Add(item)
        End Sub
        Public Sub New()

        End Sub
    End Class
    Public Sub New()

    End Sub
    Public Sub saveSettings()
        If pFileName = Nothing Then
            pFileName = Application.StartupPath & "\settings.cfg"
        End If
        Dim tXML As New System.Xml.Serialization.XmlSerializer(GetType(List(Of Section)))
        Dim tSourceFile As New System.IO.StreamWriter(pFileName)
        tXML.Serialize(tSourceFile, pSections)
        tSourceFile.Close()
    End Sub
    Public Sub loadSettings()

    End Sub
    Public ReadOnly Property sections(item As String) As Section
        Get
            For i As Integer = 0 To pSections.Count() - 1
                If pSections(i).name = item Then Return pSections(i)
            Next
            Return Nothing
        End Get
    End Property
    Public Sub addSection(name As String)
        Dim tempSection As New Section
        tempSection.name = name
        pSections.Add(tempSection)
    End Sub
End Class
Module modMain

    'Variables
    Public scales As New List(Of Scale)
    Public settings As New Settings
    Public Sub addScale(scaleName As String, scaleId As Integer, ByRef sqlConnection As sqlConnector, ByRef serialConnector As SerialPort, ByRef scales As List(Of Scale))
        Dim scale As New Scale
        scale.name = scaleName
        scale.id = scaleId
        scale.sqlConnection = sqlConnection
        scale.serialConnection = serialConnector
        scales.Add(scale)
    End Sub

    Public Sub main()

        Dim sql01 As New sqlConnector
        Dim serial01 As New SerialPort

        addScale("scale01", 178, sql01, serial01, scales)
        settings.addSection("merlegek")
        settings.addSection("sqlkapcsolatok")
        settings.sections("merlegek").addContent(scales(0))
        settings.sections("sqlkapcsolatok").addContent(sql01)
        settings.SaveSettings()

    End Sub
End Module

This is my code.

At run it stops with System.InvalidOperationException: System.ComponentModel.Component.Site tag cannot be serialized, because it's an interface. The program should basically control a few scales connected on serial port and should send the readed data to an sql database. I created the data structure. And I want to save it into an XML file (to load it up next time). I tried to find any suggestion about the problem in stack overflow, but doesn't find anything relevant...

Answer 1

As Craig

This is going to be issuing from trying to serialize serialConnection, as SerialPort inherits from System.ComponentModel.Component. I think you're going to have to mark that property/field as non-serializable and serialize enough auxiliary info to re-establish the port object on deserialization.

After I marked the problematic property with <System.Xml.Serialization.XmlIgnore> and as I made pContent Public the serialization worked.