如何：根据属性进行筛选 (XPath-LINQ to XML)

更新：November 2007

本主题演示如何获取具有指定名称、并具有一个带指定值的属性的子代元素。

XPath 表达式为：

.//Address[@Type='Shipping']

示例

本示例查找名称为 Address，Type、并具有一个带“Shipping”值的属性的子代元素。

本示例使用下面的 XML 文档：示例 XML 文件：多个采购订单 (LINQ to XML)。

XDocument po = XDocument.Load("PurchaseOrders.xml");

// LINQ to XML query
IEnumerable<XElement> list1 =
    from el in po.Descendants("Address")
    where (string)el.Attribute("Type") == "Shipping"
    select el;

// XPath expression
IEnumerable<XElement> list2 = po.XPathSelectElements(".//Address[@Type='Shipping']");

if (list1.Count() == list2.Count() &&
        list1.Intersect(list2).Count() == list1.Count())
    Console.WriteLine("Results are identical");
else
    Console.WriteLine("Results differ");
foreach (XElement el in list1)
    Console.WriteLine(el);

Dim po As XDocument = XDocument.Load("PurchaseOrders.xml")

' LINQ to XML query
Dim list1 As IEnumerable(Of XElement) = _
    From el In po...<Address> _
    Where el.@Type = "Shipping" _
    Select el

' XPath expression
Dim list2 As IEnumerable(Of XElement) = _
    po.XPathSelectElements(".//Address[@Type='Shipping']")

If (list1.Count = list2.Count And _
        list1.Intersect(list2).Count() = list1.Count()) Then
    Console.WriteLine("Results are identical")
Else
    Console.WriteLine("Results differ")
End If
For Each el As XElement In list1
    Console.WriteLine(el)
Next

本示例生成以下输出：

Results are identical
<Address Type="Shipping">
  <Name>Ellen Adams</Name>
  <Street>123 Maple Street</Street>
  <City>Mill Valley</City>
  <State>CA</State>
  <Zip>10999</Zip>
  <Country>USA</Country>
</Address>
<Address Type="Shipping">
  <Name>Cristian Osorio</Name>
  <Street>456 Main Street</Street>
  <City>Buffalo</City>
  <State>NY</State>
  <Zip>98112</Zip>
  <Country>USA</Country>
</Address>
<Address Type="Shipping">
  <Name>Jessica Arnold</Name>
  <Street>4055 Madison Ave</Street>
  <City>Seattle</City>
  <State>WA</State>
  <Zip>98112</Zip>
  <Country>USA</Country>
</Address>

请参见

概念

针对 XPath 用户的 LINQ to XML