XPathExpression クラス
アセンブリ: System.Xml (system.xml.dll 内)


このクラスは、XPathNavigator クラスの Compile メソッドの結果として返されます。これは、XPathNavigator クラスの Evaluate、Matches、Select、および SelectSingleNode 各メソッドのパラメータです。
継承時の注意 XPathExpression クラスから継承する場合は、次のメンバをオーバーライドする必要があります。-
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SetContext.

XPath の戻り値の型を使用して、XPath 式を確認する方法を次の例に示します。
Imports System Imports System.Xml Imports System.Xml.XPath Public Class XPathExpressionExample Public Shared Sub Main() Dim document As XPathDocument = New XPathDocument("contosoBooks.xml") Dim navigator As XPathNavigator = document.CreateNavigator() Dim expression1 As XPathExpression = XPathExpression.Compile(".//bk:price/text()*10") ' Returns a number. Dim expression2 As XPathExpression = XPathExpression.Compile("bk:bookstore/bk:book/bk:price") ' Returns a nodeset. Dim manager As XmlNamespaceManager = New XmlNamespaceManager(navigator.NameTable) manager.AddNamespace("bk", "http://www.contoso.com/books") expression1.SetContext(manager) expression2.SetContext(manager) Evaluate(expression1, navigator) Evaluate(expression2, navigator) End Sub Public Shared Sub Evaluate(ByVal expression As XPathExpression, ByVal navigator As XPathNavigator) Select Case expression.ReturnType Case XPathResultType.Number Console.WriteLine(navigator.Evaluate(expression)) Exit Sub Case XPathResultType.NodeSet Dim nodes As XPathNodeIterator = navigator.Select(expression) While nodes.MoveNext() Console.WriteLine(nodes.Current.ToString()) End While Case XPathResultType.Boolean If CType(navigator.Evaluate(expression), Boolean) Then Console.WriteLine("True!") End If Case XPathResultType.String Console.WriteLine(navigator.Evaluate(expression)) End Select End Sub End Class
using System; using System.Xml; using System.Xml.XPath; public class XPathExpressionExample { public static void Main() { XPathDocument document = new XPathDocument("contosoBooks.xml"); XPathNavigator navigator = document.CreateNavigator(); XPathExpression expression1 = XPathExpression.Compile(".//bk:price/text()*10"); // Returns a number. XPathExpression expression2 = XPathExpression.Compile("bk:bookstore/bk:book/bk:price"); // Returns a nodeset. XmlNamespaceManager manager = new XmlNamespaceManager(navigator.NameTable); manager.AddNamespace("bk", "http://www.contoso.com/books"); expression1.SetContext(manager); expression2.SetContext(manager); Evaluate(expression1, navigator); Evaluate(expression2, navigator); } public static void Evaluate(XPathExpression expression, XPathNavigator navigator) { switch (expression.ReturnType) { case XPathResultType.Number: Console.WriteLine(navigator.Evaluate(expression)); break; case XPathResultType.NodeSet: XPathNodeIterator nodes = navigator.Select(expression); while (nodes.MoveNext()) { Console.WriteLine(nodes.Current.ToString()); } break; case XPathResultType.Boolean: if ((bool)navigator.Evaluate(expression)) Console.WriteLine("True!"); break; case XPathResultType.String: Console.WriteLine(navigator.Evaluate(expression)); break; } } }
public ref class Sample { public: static void Evaluate( XPathExpression^ expr, XPathNavigator^ nav ) { XPathNodeIterator^ i = nav->Select(expr); switch ( expr->ReturnType ) { case XPathResultType::Number: Console::WriteLine( nav->Evaluate( expr ) ); break; case XPathResultType::NodeSet: while ( i->MoveNext() ) Console::WriteLine( i->Current ); break; case XPathResultType::Boolean: if ( *safe_cast<bool^>(nav->Evaluate( expr )) ) Console::WriteLine( "True!" ); break; case XPathResultType::String: Console::WriteLine( nav->Evaluate( expr ) ); break; } } }; int main() { XPathDocument^ doc = gcnew XPathDocument( "books.xml" ); XPathNavigator^ nav = doc->CreateNavigator(); XPathExpression^ expr1 = nav->Compile( ".//price/text()*10" ); // Returns a number. XPathExpression^ expr2 = nav->Compile( "bookstore/book/price" ); // Returns a nodeset. Sample^ MySample = gcnew Sample; MySample->Evaluate( expr1, nav ); MySample->Evaluate( expr2, nav ); }
XPathDocument doc = new XPathDocument("books.xml"); XPathNavigator nav = doc.CreateNavigator(); XPathExpression expr1 = nav.Compile(".//price/text()*10"); // Returns a number. XPathExpression expr2 = nav.Compile("bookstore/book/price"); // Returns a nodeset. Evaluate(expr1, nav); Evaluate(expr2, nav); } //main public static void Evaluate(XPathExpression expr, XPathNavigator nav) { switch (expr.get_ReturnType()) { case XPathResultType.Number: Console.WriteLine(nav.Evaluate(expr)); break; case XPathResultType.NodeSet: XPathNodeIterator i = nav.Select(expr); while (i.MoveNext()) { Console.WriteLine(i.get_Current().ToString()); } break; case XPathResultType.Boolean: if (System.Convert.ToBoolean(nav.Evaluate(expr))) { Console.WriteLine("True!"); } break; case XPathResultType.String: Console.WriteLine(nav.Evaluate(expr)); break; } } //Evaluate
この例では、入力として、contosoBooks.xml というファイルを使用しています。
<bookstore xmlns="http://www.contoso.com/books"> <book genre="autobiography" publicationdate="1981-03-22" ISBN="1-861003-11-0"> <title>The Autobiography of Benjamin Franklin</title> <author> <first-name>Benjamin</first-name> <last-name>Franklin</last-name> </author> <price>8.99</price> </book> <book genre="novel" publicationdate="1967-11-17" ISBN="0-201-63361-2"> <title>The Confidence Man</title> <author> <first-name>Herman</first-name> <last-name>Melville</last-name> </author> <price>11.99</price> </book> <book genre="philosophy" publicationdate="1991-02-15" ISBN="1-861001-57-6"> <title>The Gorgias</title> <author> <name>Plato</name> </author> <price>9.99</price> </book> </bookstore>

System.Xml.XPath.XPathExpression


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