HOW TO：尋找前面同層級 (XPath-LINQ to XML)

這個主題會比較 XPath preceding-sibling 座標軸與 LINQ to XML 子系 XNode.ElementsBeforeSelf 座標軸。

XPath 運算式為：

preceding-sibling::*

請注意，XPathSelectElements 和 XNode.ElementsBeforeSelf 的結果都會以文件的順序排列。

範例

下列範例會尋找 FullAddress 項目，然後使用 preceding-sibling 座標軸擷取先前的項目。

此範例使用下列 XML 文件：XML 範例檔：客戶和訂單 (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

這個範例產生下列輸出：

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

請參閱

概念

適用於 XPath 使用者的 LINQ to XML