無法將“System.Object”型別的物件轉換為型別（MyClass）Vb.Net

我正在使用此代碼將我的類“設備”的物件存盤到物件，但我得到了“system.invalidcastexception”例外。我在其他課程中以相同的方式投射它，它在那里作業，但在這里它不作業

Public Class Device
Inherits MainDevice

Private TestData As New SortedList(Of Integer, DataVPAA)
Public Sub New(ByVal version As String, ByVal System As String, ByVal IdNumber As UInteger, ByVal Serial As String)
    DataVersion = version
    SystemVersion = System
    Serial_Number = Serial
    IdentNumber = IdNumber

這是我得到錯誤的地方

    Dim obj As Object
    obj = LoadXml(GetType(Device), Path)
    If obj Is Nothing Then
        ' Some Logic Here
    Else
        Dim dev As New Device
        dev = CType(obj, Device) '**system.invalidcastexception**

        Me.TestData = dev.TestData
        ' Some Logic Here
    End If

End Sub
End Class

加載函式

Function LoadXML(ByVal DeviceType As Type, ByVal Path As String) As Object
Dim obj As New Object
Dim XMLFilePath As String
Dim xmlreader As XmlReader

If Me.GetType = GetType(ABCDevice) Or Me.GetType = GetType(CVDevice) Or Me.GetType = GetType(CV2Device) Then
    XMLFilePath = Path   "\"   strIdentNr   "_"   Serial_Number   ".xml"
Else
    XMLFilePath = Path   "\"   IdentNumber.ToString   "_"   Serial_Number   ".xml"
End If

'Check if File exists
If File.Exists(XMLFilePath) Then
    Dim fs As New FileStream(XMLFilePath, FileMode.Open, FileAccess.Read)
    xmlreader = XmlReader.Create(fs)
    Try 'Try to deserialize to object
        Dim xml_deserializer As New Serialization.XmlSerializer(DeviceType)
        If xml_deserializer.CanDeserialize(xmlreader) Then

            obj = xml_deserializer.Deserialize(xmlreader)

        End If
    Catch ex As Exception
        MessageBox.Show("XML Deserializer Error: "   ex.Message)
    End Try
    fs.Close()
    Return obj
Else : Return Nothing
End If
End Function

我嘗試使用不同的方法（例如 directcast 和其他方法）進行投射，但我遇到了同樣的例外。

uj5u.com熱心網友回復：

您可以使 LoadXml 通用并始終回傳您想要的型別。如

Function LoadXml(Of T)(path As String) As T
    Dim obj As T = Nothing
    Dim XMLFilePath As String

    If Me.GetType = GetType(ABCDevice) Or Me.GetType = GetType(CVDevice) Or Me.GetType = GetType(CV2Device) Then
        XMLFilePath = path   "\"   strIdentNr   "_"   Serial_Number   ".xml"
    Else
        XMLFilePath = path   "\"   IdentNumber.ToString   "_"   Serial_Number   ".xml"
    End If

    'Check if File exists
    If File.Exists(XMLFilePath) Then
        Using fs As New FileStream(XMLFilePath, FileMode.Open, FileAccess.Read)
            Using reader = XmlReader.Create(fs)
                Try 'Try to deserialize to object
                    Dim xml_deserializer As New Serialization.XmlSerializer(GetType(T))
                    If xml_deserializer.CanDeserialize(reader) Then
                        obj = xml_deserializer.Deserialize(reader)
                    End If
                Catch ex As Exception
                    MessageBox.Show("XML Deserializer Error: "   ex.Message)
                End Try
            End Using
        End Using
    End If
    Return obj
End Function

Dim dev = LoadXml(Of Device)("path")

現在 dev 保證是一個設備。如果什么都沒有，那就失敗了

標籤：VB.net 例外 铸件

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