VB.NET通過XML循環存儲在單例中

Question

我在遍歷XML文件並將值存儲在單例中時遇到問題

我的XML看起來像這樣

<values>
    <value></value>
    <value>$1</value>           
    <value>$5,000</value>       
    <value>$10,000</value>      
    <value>$15,000</value>      
    <value>$25,000</value>      
    <value>$50,000</value>      
    <value>$75,000</value>      
    <value>$100,000</value>     
    <value>$250,000</value>     
    <value>$500,000</value>     
    <value>$750,000</value>     
    <value>$1,000,000</value>   
    <value>$1,250,000</value>   
    <value>$1,500,000</value>   
    <value>$1,750,000</value>   
    <value>$2,000,000</value>   
    <value>$2,500,000</value>   
    <value>$3,000,000</value>   
    <value>$4,000,000</value>   
    <value>$5,000,000</value>   
    <value>$7,500,000</value>   
    <value>$10,000,000</value>  
    <value>$15,000,000</value>  
    <value>$25,000,000</value>  
    <value>$50,000,000</value>  
    <value>$100,000,000</value> 
    <value>$100,000,000+</value>
</values>

我的功能看起來像這樣

Public Class LoadValues
    Private Shared SearchValuesInstance As List(Of SearchValues) = Nothing

    Public Shared ReadOnly Property LoadSearchValues As List(Of SearchValues)
        Get
            Dim sv As New List(Of SearchValues)

            If SearchValuesInstance Is Nothing Then
                Dim objDoc As XmlDocument = New XmlDataDocument
                Dim objRdr As XmlTextReader = New XmlTextReader(HttpContext.Current.Server.MapPath("~/App_Data/Search-Values.xml"))
                objRdr.Read()
                objDoc.Load(objRdr)

                Dim root As XmlElement = objDoc.DocumentElement
                Dim itemNodes As XmlNodeList = root.SelectNodes("/values")

                For Each n As XmlNode In itemNodes
                    sv.Add(New SearchValues(n("@value").InnerText, n("@value").InnerText))
                Next
                SearchValuesInstance = sv

            Else : sv = SearchValuesInstance
            End If

            Return sv
        End Get
    End Property

End Class

我的問題是我在sv.Add(New SearchValues(n("@value").InnerText, n("@value").InnerText))行上得到的object not set to an instance of an object 。

Answer 1

好的，我似乎找到了答案。 希望這將幫助下一個有同樣問題的人。

Public Class LoadValues
    Private Shared SearchValuesInstance As List(Of SearchValues) = Nothing

    Public Shared ReadOnly Property LoadSearchValues As List(Of SearchValues)
        Get
            Dim sv As New List(Of SearchValues)

            If SearchValuesInstance Is Nothing Then

                Dim objDoc As XmlDocument = New XmlDataDocument
                objDoc.Load(HttpContext.Current.Server.MapPath("~/App_Data/Search-Values.xml"))

                Dim root As XmlNode = objDoc.DocumentElement
                Dim nodelist As XmlNodeList = root.SelectNodes("/values/value")

                Dim value As Double

                For Each n As XmlNode In nodelist
                    value = If(BizHelper.ConvertToDouble(n.InnerText) Is Nothing, 0, BizHelper.ConvertToDouble(n.InnerText))
                    sv.Add(New SearchValues(n.InnerText, value))
                Next

                SearchValuesInstance = sv

            Else : sv = SearchValuesInstance
            End If

            Return sv
        End Get
    End Property

    Public Shared Sub DisposeSearchValues()
        SearchValuesInstance = Nothing
    End Sub

End Class