ツリー内のすべてのノードを一覧表示すると便利な場合があります。 これは、メソッドやプロパティがツリーに及ぼす影響を確認するときに役立ちます。 すべてのノードをテキスト形式で一覧表示する方法の 1 つは、ツリー内の任意のノードを正確かつ明確に識別する XPath 式を生成することです。
LINQ to XML を使用して XPath 式を実行する方法は特に有効ではありません。 XPath 式は LINQ to XML クエリよりパフォーマンスが低く、LINQ to XML クエリの方がはるかに強力です。 ただし、XPath 式は、XML ツリー内のノードを識別する手段としては有効です。
使用例
この例では、XML ツリー内の任意のノードを表す特定の XPath 式を生成する、GetXPath という名前の関数を示します。 この関数は、ノードが名前空間に含まれている場合でも、適切な XPath 式を生成します。 XPath 式は、名前空間プレフィックスを使用して生成されます。
この例では、複数の種類のノード例を含む小さな XML ツリーを作成します。 次に、子孫ノードを反復処理し、各ノードを表す XPath 式を出力します。
XML 宣言がツリー内のノードではないことがわかります。
複数の種類のノードを含む XML ファイルを次に示します。
<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<?target data?>
<Root AttName="An Attribute" xmlns:aw="https://www.adventure-works.com">
<!--This is a comment-->
<Child>Text</Child>
<Child>Other Text</Child>
<ChildWithMixedContent>text<b>BoldText</b>otherText</ChildWithMixedContent>
<aw:ElementInNamespace>
<aw:ChildInNamespace />
</aw:ElementInNamespace>
</Root>
上記の XML ツリー内のノードを表す XPath 式の一覧を次に示します。
/processing-instruction()
/Root
/Root/@AttName
/Root/@xmlns:aw
/Root/comment()
/Root/Child[1]
/Root/Child[1]/text()
/Root/Child[2]
/Root/Child[2]/text()
/Root/ChildWithMixedContent
/Root/ChildWithMixedContent/text()[1]
/Root/ChildWithMixedContent/b
/Root/ChildWithMixedContent/b/text()
/Root/ChildWithMixedContent/text()[2]
/Root/aw:ElementInNamespace
/Root/aw:ElementInNamespace/aw:ChildInNamespace
public static class MyExtensions
{
private static string GetQName(XElement xe)
{
string prefix = xe.GetPrefixOfNamespace(xe.Name.Namespace);
if (xe.Name.Namespace == XNamespace.None || prefix == null)
return xe.Name.LocalName.ToString();
else
return prefix + ":" + xe.Name.LocalName.ToString();
}
private static string GetQName(XAttribute xa)
{
string prefix =
xa.Parent.GetPrefixOfNamespace(xa.Name.Namespace);
if (xa.Name.Namespace == XNamespace.None || prefix == null)
return xa.Name.ToString();
else
return prefix + ":" + xa.Name.LocalName;
}
private static string NameWithPredicate(XElement el)
{
if (el.Parent != null && el.Parent.Elements(el.Name).Count() != 1)
return GetQName(el) + "[" +
(el.ElementsBeforeSelf(el.Name).Count() + 1) + "]";
else
return GetQName(el);
}
public static string StrCat<T>(this IEnumerable<T> source,
string separator)
{
return source.Aggregate(new StringBuilder(),
(sb, i) => sb
.Append(i.ToString())
.Append(separator),
s => s.ToString());
}
public static string GetXPath(this XObject xobj)
{
if (xobj.Parent == null)
{
XDocument doc = xobj as XDocument;
if (doc != null)
return ".";
XElement el = xobj as XElement;
if (el != null)
return "/" + NameWithPredicate(el);
// the XPath data model does not include white space text nodes
// that are children of a document, so this method returns null.
XText xt = xobj as XText;
if (xt != null)
return null;
XComment com = xobj as XComment;
if (com != null)
return
"/" +
(
com
.Document
.Nodes()
.OfType<XComment>()
.Count() != 1 ?
"comment()[" +
(com
.NodesBeforeSelf()
.OfType<XComment>()
.Count() + 1) +
"]" :
"comment()"
);
XProcessingInstruction pi = xobj as XProcessingInstruction;
if (pi != null)
return
"/" +
(
pi.Document.Nodes()
.OfType<XProcessingInstruction>()
.Count() != 1 ?
"processing-instruction()[" +
(pi
.NodesBeforeSelf()
.OfType<XProcessingInstruction>()
.Count() + 1) +
"]" :
"processing-instruction()"
);
return null;
}
else
{
XElement el = xobj as XElement;
if (el != null)
{
return
"/" +
el
.Ancestors()
.InDocumentOrder()
.Select(e => NameWithPredicate(e))
.StrCat("/") +
NameWithPredicate(el);
}
XAttribute at = xobj as XAttribute;
if (at != null)
return
"/" +
at
.Parent
.AncestorsAndSelf()
.InDocumentOrder()
.Select(e => NameWithPredicate(e))
.StrCat("/") +
"@" + GetQName(at);
XComment com = xobj as XComment;
if (com != null)
return
"/" +
com
.Parent
.AncestorsAndSelf()
.InDocumentOrder()
.Select(e => NameWithPredicate(e))
.StrCat("/") +
(
com
.Parent
.Nodes()
.OfType<XComment>()
.Count() != 1 ?
"comment()[" +
(com
.NodesBeforeSelf()
.OfType<XComment>()
.Count() + 1) + "]" :
"comment()"
);
XCData cd = xobj as XCData;
if (cd != null)
return
"/" +
cd
.Parent
.AncestorsAndSelf()
.InDocumentOrder()
.Select(e => NameWithPredicate(e))
.StrCat("/") +
(
cd
.Parent
.Nodes()
.OfType<XText>()
.Count() != 1 ?
"text()[" +
(cd
.NodesBeforeSelf()
.OfType<XText>()
.Count() + 1) + "]" :
"text()"
);
XText tx = xobj as XText;
if (tx != null)
return
"/" +
tx
.Parent
.AncestorsAndSelf()
.InDocumentOrder()
.Select(e => NameWithPredicate(e))
.StrCat("/") +
(
tx
.Parent
.Nodes()
.OfType<XText>()
.Count() != 1 ?
"text()[" +
(tx
.NodesBeforeSelf()
.OfType<XText>()
.Count() + 1) + "]" :
"text()"
);
XProcessingInstruction pi = xobj as XProcessingInstruction;
if (pi != null)
return
"/" +
pi
.Parent
.AncestorsAndSelf()
.InDocumentOrder()
.Select(e => NameWithPredicate(e))
.StrCat("/") +
(
pi
.Parent
.Nodes()
.OfType<XProcessingInstruction>()
.Count() != 1 ?
"processing-instruction()[" +
(pi
.NodesBeforeSelf()
.OfType<XProcessingInstruction>()
.Count() + 1) + "]" :
"processing-instruction()"
);
return null;
}
}
}
class Program
{
static void Main(string[] args)
{
XNamespace aw = "https://www.adventure-works.com";
XDocument doc = new XDocument(
new XDeclaration("1.0", "utf-8", "yes"),
new XProcessingInstruction("target", "data"),
new XElement("Root",
new XAttribute("AttName", "An Attribute"),
new XAttribute(XNamespace.Xmlns + "aw", aw.ToString()),
new XComment("This is a comment"),
new XElement("Child",
new XText("Text")
),
new XElement("Child",
new XText("Other Text")
),
new XElement("ChildWithMixedContent",
new XText("text"),
new XElement("b", "BoldText"),
new XText("otherText")
),
new XElement(aw + "ElementInNamespace",
new XElement(aw + "ChildInNamespace")
)
)
);
doc.Save("Test.xml");
Console.WriteLine(File.ReadAllText("Test.xml"));
Console.WriteLine("------");
foreach (XObject obj in doc.DescendantNodes())
{
Console.WriteLine(obj.GetXPath());
XElement el = obj as XElement;
if (el != null)
foreach (XAttribute at in el.Attributes())
Console.WriteLine(at.GetXPath());
}
}
}
Module Module1
<System.Runtime.CompilerServices.Extension()> _
Private Function StrCat(Of T)(ByVal source As IEnumerable(Of T), _
ByVal separator As String) As String
Return _
source.Aggregate(New StringBuilder(), _
Function(sb, i) sb _
.Append(i.ToString()) _
.Append(separator), _
Function(s) s.ToString())
End Function
<System.Runtime.CompilerServices.Extension()> _
Public Function GetXPath(ByVal xobj As XObject) As String
Dim retStr As String
If xobj.Parent Is Nothing Then
Dim doc As XDocument = TryCast(xobj, XDocument)
If doc IsNot Nothing Then
Return "."
End If
Dim el As XElement = TryCast(xobj, XElement)
If el IsNot Nothing Then
Return ("/" & NameWithPredicate(el))
End If
' The XPath data model does not include white space text nodes
' that are children of a document, so this method returns null.
Dim xt As XText = TryCast(xobj, XText)
If xt IsNot Nothing Then
Return Nothing
End If
Dim com As XComment = TryCast(xobj, XComment)
If com IsNot Nothing Then
If com.Document().Nodes().OfType(Of XComment)().Count() <> 1 Then
Return "/comment()[" & (com.NodesBeforeSelf().OfType _
(Of XComment)().Count() + 1) & "]"
Else
Return "/comment()"
End If
End If
Dim pi As XProcessingInstruction = TryCast(xobj, XProcessingInstruction)
If pi IsNot Nothing Then
If pi.Document.Nodes().OfType(Of XProcessingInstruction)(). _
Count() <> 1 Then
Return "/processing-instruction()[" & _
(pi.NodesBeforeSelf().OfType(Of XProcessingInstruction)() _
.Count() + 1) & "]"
Else
Return "/processing-instruction()"
End If
End If
Else
Dim el As XElement = TryCast(xobj, XElement)
If el IsNot Nothing Then
Return "/" & el.Ancestors().InDocumentOrder(). _
Select(Function(e) NameWithPredicate(e)) _
.StrCat("/") & NameWithPredicate(el)
End If
Dim at As XAttribute = TryCast(xobj, XAttribute)
If at IsNot Nothing Then
Return "/" & at.Parent().AncestorsAndSelf().InDocumentOrder(). _
Select(Function(e) NameWithPredicate(e)).StrCat("/") & _
"@" & GetQName(at)
End If
Dim com As XComment = TryCast(xobj, XComment)
If com IsNot Nothing Then
retStr = "/" & com.Parent.AncestorsAndSelf().InDocumentOrder(). _
Select(Function(e) NameWithPredicate(e)).StrCat("/") & "comment()"
If com.Parent().Nodes().OfType(Of XComment)().Count() <> 1 Then
retStr &= "[" & (com.NodesBeforeSelf().OfType(Of XComment)().Count() + 1) & "]"
End If
Return retStr
End If
Dim cd As XCData = TryCast(xobj, XCData)
If cd IsNot Nothing Then
retStr = "/" & cd.Parent.AncestorsAndSelf().InDocumentOrder(). _
Select(Function(e) NameWithPredicate(e)).StrCat("/") & "text()"
If cd.Parent.Nodes().OfType(Of XText)().Count() <> 1 Then
retStr &= "[" & (cd.NodesBeforeSelf().OfType(Of XText)(). _
Count() + 1) & "]"
End If
Return retStr
End If
Dim tx As XText = TryCast(xobj, XText)
If tx IsNot Nothing Then
retStr = "/" & tx.Parent.AncestorsAndSelf().InDocumentOrder(). _
Select(Function(e) NameWithPredicate(e)).StrCat("/") & "text()"
If tx.Parent.Nodes().OfType(Of XText)().Count() <> 1 Then
retStr &= "[" & (tx.NodesBeforeSelf().OfType(Of XText)(). _
Count() + 1) & "]"
End If
Return retStr
End If
Dim pi As XProcessingInstruction = TryCast(xobj, XProcessingInstruction)
If pi IsNot Nothing Then
retStr = "/" & pi.Parent.AncestorsAndSelf().InDocumentOrder(). _
Select(Function(e) NameWithPredicate(e)). _
StrCat("/") & "processing-instruction()"
If pi.Parent.Nodes().OfType(Of XProcessingInstruction)().Count() <> 1 Then
retStr &= "[" & (pi.NodesBeforeSelf().OfType(Of XProcessingInstruction)(). _
Count() + 1) & "]"
End If
End If
End If
Return Nothing
End Function
Private Function GetQName(ByVal xe As XElement) As String
Dim prefix As String = xe.GetPrefixOfNamespace(xe.Name.Namespace)
If xe.Name.Namespace = XNamespace.None Or prefix Is Nothing Then
Return xe.Name.LocalName.ToString()
Else
Return prefix + ":" & xe.Name.LocalName.ToString()
End If
End Function
Private Function GetQName(ByVal xa As XAttribute) As String
Dim prefix As String = _
xa.Parent.GetPrefixOfNamespace(xa.Name.Namespace)
If xa.Name.Namespace = XNamespace.None Or prefix Is Nothing Then
Return xa.Name.ToString()
Else
Return prefix + ":" & xa.Name.LocalName
End If
End Function
Public Function NameWithPredicate(ByVal el As XElement) As String
If el.Parent IsNot Nothing AndAlso el.Parent.Elements(el.Name).Count() <> 1 Then
Return GetQName(el) + "[" & _
(el.ElementsBeforeSelf(el.Name).Count() + 1) & "]"
Else
Return GetQName(el)
End If
End Function
Sub Main()
Dim aw As XNamespace = "https://www.adventure-works.com"
Dim doc As XDocument = _
<?xml version='1.0' encoding="utf-8" standalone='yes'?>
<?target data?>
<Root AttName='An Attribute' xmlns:aw='https://www.adventure-works.com'>
<!--This is a comment-->
<Child>Text</Child>
<Child>Other Text</Child>
<ChildWithMixedContent>text<b>BoldText</b>otherText</ChildWithMixedContent>
<aw:ElementInNamespace>
<aw:ChildInNamespace/>
</aw:ElementInNamespace>
</Root>
doc.Save("Test.xml")
Console.WriteLine(File.ReadAllText("Test.xml"))
Console.WriteLine("------")
For Each obj As XObject In doc.DescendantNodes()
Console.WriteLine(obj.GetXPath())
Dim el As XElement = TryCast(obj, XElement)
If el IsNot Nothing Then
For Each at As XAttribute In el.Attributes()
Console.WriteLine(at.GetXPath())
Next
End If
Next
End Sub
End Module
この例を実行すると、次の出力が生成されます。
<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<?target data?>
<Root AttName="An Attribute" xmlns:aw="https://www.adventure-works.com">
<!--This is a comment-->
<Child>Text</Child>
<Child>Other Text</Child>
<ChildWithMixedContent>text<b>BoldText</b>otherText</ChildWithMixedContent>
<aw:ElementInNamespace>
<aw:ChildInNamespace />
</aw:ElementInNamespace>
</Root>
------
/processing-instruction()
/Root
/Root/@AttName
/Root/@xmlns:aw
/Root/comment()
/Root/Child[1]
/Root/Child[1]/text()
/Root/Child[2]
/Root/Child[2]/text()
/Root/ChildWithMixedContent
/Root/ChildWithMixedContent/text()[1]
/Root/ChildWithMixedContent/b
/Root/ChildWithMixedContent/b/text()
/Root/ChildWithMixedContent/text()[2]
/Root/aw:ElementInNamespace
/Root/aw:ElementInNamespace/aw:ChildInNamespace