protobuf net构造函数重写反序列化值

我正在序列化一个对象,当加载回时,如果缺少一个字段,我想设置一个特定的值。例如,如果在版本2上添加了一个字段,则在加载由版本1生成的文件时,我想设置一个值。

<ProtoContract()>
Public Class Settings

    '  ... other members

    <ProtoMember(33)>
    Public AutoZoom As Boolean 


    'Load from a file
    Friend Shared Function Load(filePath as string) As Settings

        Dim result As Settings

        Try
            If IO.File.Exists(filePath) Then
                Using s As New IO.FileStream(filePath, IO.FileMode.Open)
                    result = Serializer.Deserialize(Of Settings)(s)
                End Using
            Else
                result = CreateNew()
            End If
        Catch ex As Exception
            result = CreateNew()
        End Try

        Return result

    End Function

    Public Shared Function CreateNew() As Settings

        Dim n = New Settings()
        Return n

    End Function        

    Private Sub New()

        AutoZoom = TRUE

    end sub         

End Class

我试图使用构造函数,认为它会在字段反序列化之前运行。但是,当从序列化文件加载对象时,某些字段将使用文件内的值加载,但其他一些字段将保留构造函数设置的值,并且文件内的值将被忽略。

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