閱讀的XMLDocument具有相同的元素名稱

Question

我要讀XML文檔數據，是在這裏：

<root> 
    <cartype>Mercedes</cartype> 
    <production>2005</production> 
    <fuel>Diesel</fuel> 
    <color>Red</color> 
    <services> 
    <service> 
     <year>2006</year> 
     <km>47800</km> 
     <city>Stuttgart</city> 
    </service> 
    <service> 
     <year>2007</year> 
     <km>92125</km> 
     <city>FFM</city> 
    </service> 
    <service> 
     <km>180420</km> 
     <year>2009</year> 
     <city>Hannover</city> 
    </service> 
    </services> 
    <condition>Good</condition> 
</root> 

然後我讀它是這樣：

Dim cartype As String 
Dim fuel As String 
Dim production As String 
Dim color As String 
Dim serviceyear() As String = {"", "", ""} 
Dim servicekm() As String = {"", "", ""} 
Dim sevicecity() As String = {"", "", ""} 
Dim doc As XmlDocument = New XmlDocument() 

doc.Load("mercedes.xml") 
Dim root As XmlElement = doc.DocumentElement 

Dim node As XmlNode = root.SelectSingleNode("production") 
If Not node Is Nothing Then production = node.InnerText 

node = root.SelectSingleNode("cartype") 
If Not node Is Nothing Then cartype = node.InnerText 

node = root.SelectSingleNode("fuel") 
If Not node Is Nothing Then fuel = node.InnerText 

node = root.SelectSingleNode("color") 
If Not node Is Nothing Then color = node.InnerText 

node = root.SelectSingleNode("services/service/year") '' first service year 
If Not node Is Nothing Then serviceyear(0) = node.InnerText 

node = root.SelectSingleNode("services/service/year") '' second service year 
If Not node Is Nothing Then serviceyear(1) = node.InnerText 

具有獨特的元素名稱讀節點是確定的，但我不知道如何讀取數組中的所有「服務」，因爲顯示的代碼只讀取第一個服務。服務可能從0到未定義的數字。函數必須儘可能快，因爲大量的xml必須在可能的時間內被減少。

Answer 1

讀取變量數<service>的元素，你將需要使用SelectNodes而不是SelectSingleNode：

Dim services = root.SelectNodes("services/service") 

然後，您可以遍歷<service>節點：

For Each service In services 
    If service("year") IsNot Nothing Then 
     Dim year = service("year").InnerText 
    End If 
Next 

個人而言，我會使用LINQ to XML解析文件（但這可能是因爲我癡迷於LINQ的所有東西！）。結合VB.NET對XML Literals的支持，它使得一些非常漂亮的代碼（恕我直言）。

這是一個完整的例子，你可以粘貼到LINQPad。

Sub Main 
    ' Use XElememt.Load(fileName) to load from file 
    Dim xml = 
    <root> 
     <cartype>Mercedes</cartype> 
     <production>2005</production> 
     <fuel>Diesel</fuel> 
     <color>Red</color> 
     <services> 
      <service> 
       <year>2006</year> 
       <km>47800</km> 
       <city>Stuttgart</city> 
      </service> 
      <service> 
       <year>2007</year> 
       <km>92125</km> 
       <city>FFM</city> 
      </service> 
      <service> 
       <km>180420</km> 
       <year>2009</year> 
       <city>Hannover</city> 
      </service> 
     </services> 
     <condition>Good</condition> 
    </root> 
    Dim history = New ServiceHistory() With { 
     .CarType = xml.<cartype>.Value, 
     .Production = xml.<production>.Value, 
     .Fuel = xml.<fuel>.Value, 
     .Color = xml.<color>.Value, 
     .Condition = xml.<condition>.Value, 
     .Services = (
      From svc In xml.<services>.<service> 
      Select New Service() With { 
       .Year = svc.<year>.Value, 
       .KM = svc.<km>.Value, 
       .City = svc.<city>.Value 
      } 
     ).ToList() 
    } 
    history.Dump() 
End Sub 

' Define other methods and classes here 
Public Class ServiceHistory 
    Public Property CarType As String 
    Public Property Production As String 
    Public Property Fuel As String 
    Public Property Color As String 
    Public Property Condition As String 
    Public Property Services As List(Of Service) 
End Class 

Public Class Service 
    Public Property Year As String 
    Public Property KM As String 
    Public Property City As String 
End Class 

這給你以下幾點：

Answer 2

嘗試LINQ它會更容易解析XML： 它必須是類似的東西：

xelement = XElement.Load(file); 
services = xelement.Element("services").Elements("service");