Vb.Net实例化一个类的属性，它是一个不同类的数组

Question

这是为了对 Xml 对象进行序列化和反序列化

<XmlRoot("orderadd")>
<Serializable()> _
Public Class clsSMsgRequestMessage
    <XmlElementAttribute()> Public Property ordertype() As String
    <XmlElementAttribute()> Public Property vehicleid() As String
    <XmlElementAttribute()> Public Property orderpriority() As String
    <XmlElementAttribute("orderpart")> Public Property orderpart() As RequestMessageOrderaddOrderpart()
    <XmlAttributeAttribute()> Public Property clientid() As String
    <XmlAttributeAttribute()> Public Property transactionid() As String
    <XmlAttributeAttribute()> Public Property numberoforderparts() As String

    Public Sub New()
    End Sub
End Class

Public Class RequestMessageOrderaddOrderpart
    <XmlElementAttribute()> Public Property operation() As String
    <XmlElementAttribute()> Public Property location() As String
    <XmlElementAttribute()> Public Property loadtype() As String
    <XmlAttributeAttribute()> Public Property orderpartnumber() As String

    Public Sub New()
    End Sub

End Class

这适用于反序列化，但现在我正在尝试正确创建此对象，以便可以将其序列化回 XML 对象。

Dim anotherTest As clsSMsgRequestMessage = New clsSMsgRequestMessage()
Dim testOrderPart1 As New RequestMessageOrderaddOrderpart


anotherTest.clientid = "data"
anotherTest.orderpriority = "data"
anotherTest.ordertype = "data"
anotherTest.transactionid = "data"
anotherTest.vehicleid = "data"
anotherTest.numberoforderparts = "data"

testOrderPart1.loadtype = "data"
testOrderPart1.location = "data"
testOrderPart1.operation = "data"
testOrderPart1.orderpartnumber = "data"


anotherTest.orderpart(0) = testOrderPart1

这里的最后一行不起作用，因为 anotherTest.orderpart(0) 尚未实例化。但我不知道如何实例化它，因为

anotherTest.orderpart(0) = New RequestMessageOrderaddOrderPart

仍然返回“对象引用未设置为对象的实例。”

anotherTest.orderpart = New RequestMessageOrderaddOrderPart

返回“类型的值不能转换为'一维数组”

我认为我在自己实例化它方面走在正确的轨道上，就像我正在使用“testOrderPart1”一样，但我不知道如何将它链接到我的 anotherTest.orderpart

请帮忙！

Answer 1

你必须先初始化你的数组属性：

anotherTest.orderpart = New RequestMessageOrderaddOrderPart(10) {}

10 是数组大小。

之后你就可以设置第一个数组元素了：

anotherTest.orderpart(0) = New RequestMessageOrderaddOrderPart

更新

但是，我认为您应该将您的属性声明更改为List(Of RequestMessageOrderaddOrderPart)。使用列表，您不必指定项目数：

anotherTest.orderpart = New List(Of RequestMessageOrderaddOrderPart)()

添加项目真的很容易：

anotherTest.orderpart.Add(new RequestMessageOrderaddOrderPart())

您仍然可以使用索引器获取/修改项目：

Dim firstItem = anotherTest.orderpart(0)

当然，该项目必须先使用Add 方法插入。

List(Of T) 也可以很好地用于序列化。