Gewusst wie: Auflisten aller Knoten in einer Struktur
Aktualisiert: November 2007
Manchmal ist es hilfreich, alle in einer Struktur vorhandenen Knoten aufzulisten. Dies kann sinnvoll sein, wenn Sie genau verstehen möchten, wie sich eine Methode oder eine Eigenschaft auf die Struktur auswirkt. Eine Möglichkeit, alle Knoten in Textform aufzulisten, besteht darin, einen XPath-Ausdruck zu generieren, der exakt und spezifisch jeden Knoten in der Struktur identifiziert.
Das Ausführen von XPath-Ausdrücken mit LINQ to XML ist nicht besonders hilfreich. XPath-Ausdrücke verfügen über eine schlechtere Leistung als LINQ to XML-Abfragen, und LINQ to XML-Abfragen sind deutlich leistungsfähiger. Zur Identifizierung der Knoten in der XML-Struktur eignet sich XPath aber gut.
Beispiel
Dieses Beispiel zeigt eine Funktion mit dem Namen GetXPath, die für jeden Knoten in der XML-Struktur einen spezifischen XPath-Ausdruck generiert. Sie generiert auch dann entsprechende XPath-Ausdrücke, wenn sich Knoten in einem Namespace befinden. Die XPath-Ausdrücke werden unter Verwendung von Namespacepräfixen generiert.
Im Beispiel wird dann eine kleine XML-Struktur erstellt, die ein Beispiel für mehrere Typen von Knoten enthält. Anschließend durchläuft das Beispiel die Nachfolgerknoten und gibt für jeden Knoten den XPath-Ausdruck aus.
Sie werden feststellen, dass die XML-Deklaration kein Knoten in der Struktur ist.
Es folgt eine XML-Datei, die mehrere Typen von Knoten enthält:
<?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>
Es folgt die Liste der in der oben erwähnten XML-Struktur vorhandenen Knoten, ausgedrückt als XPath-Ausdrücke:
/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
Dieses Beispiel führt zur folgenden Ausgabe:
<?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