如何：查找前面的同级 (XPath-LINQ to XML)

更新：November 2007

本主题将 XPath preceding-sibling 轴与 LINQ to XML 子 XNode.ElementsBeforeSelf 轴进行比较。

XPath 表达式为：

preceding-sibling::*

请注意，XPathSelectElements 和 XNode.ElementsBeforeSelf 的结果都遵循文档顺序。

示例

下面的示例查找 FullAddress 元素，然后使用 preceding-sibling 轴检索前面的元素。

本示例使用下面的 XML 文档：示例 XML 文件：客户和订单 (LINQ to XML)。

XElement co = XElement.Load("CustomersOrders.xml");

XElement add = co.Element("Customers").Element("Customer").Element("FullAddress");

// LINQ to XML query
IEnumerable<XElement> list1 = add.ElementsBeforeSelf();

// XPath expression
IEnumerable<XElement> list2 = add.XPathSelectElements("preceding-sibling::*");

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 list2)
    Console.WriteLine(el);

Dim co As XElement = XElement.Load("CustomersOrders.xml")
Dim add As XElement = co.<Customers>.<Customer>. _
        <FullAddress>.FirstOrDefault

' LINQ to XML query
Dim list1 As IEnumerable(Of XElement) = add.ElementsBeforeSelf()

' XPath expression
Dim list2 As IEnumerable(Of XElement) = add.XPathSelectElements("preceding-sibling::*")

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 list2
    Console.WriteLine(el)
Next

本示例生成以下输出：

Results are identical
<CompanyName>Great Lakes Food Market</CompanyName>
<ContactName>Howard Snyder</ContactName>
<ContactTitle>Marketing Manager</ContactTitle>
<Phone>(503) 555-7555</Phone>

请参见

概念

针对 XPath 用户的 LINQ to XML