XmlDsigXPathTransform Clase

Definición

Espacio de nombres:

System.Security.Cryptography.Xml

Ensamblado:

System.Security.Cryptography.Xml.dll

Representa la transformación XPath para una firma digital que define W3C.

public ref class XmlDsigXPathTransform : System::Security::Cryptography::Xml::Transform

public class XmlDsigXPathTransform : System.Security.Cryptography.Xml.Transform

type XmlDsigXPathTransform = class
    inherit Transform

Public Class XmlDsigXPathTransform
Inherits Transform

Herencia

Object

Transform

XmlDsigXPathTransform

Ejemplos

Esta sección contiene dos ejemplos de código. En el primer ejemplo de código se muestra cómo firmar y comprobar un documento XML mediante la clase con una firma de XmlDsigXPathTransform sobre. En este ejemplo se firma un documento XML y se guarda la firma en un nuevo documento XML. En el segundo ejemplo de código se muestra cómo llamar a miembros de la XmlDsigXPathTransform clase .

Ejemplo 1

//
// This example signs an XML file using an
// envelope signature. It then verifies the 
// signed XML.
//
#using <System.Xml.dll>
#using <System.Security.dll>
#using <System.dll>

using namespace System;
using namespace System::Security::Cryptography;
using namespace System::Security::Cryptography::X509Certificates;
using namespace System::Security::Cryptography::Xml;
using namespace System::Text;
using namespace System::Xml;

// Create the XML that represents the transform.
static XmlDsigXPathTransform^ CreateXPathTransform( String^ XPathString )
{
   
   // Create a new XMLDocument object.
   XmlDocument^ doc = gcnew XmlDocument;
   
   // Create a new XmlElement.
   XmlElement^ xPathElem = doc->CreateElement( L"XPath" );
   
   // Set the element text to the value
   // of the XPath string.
   xPathElem->InnerText = XPathString;
   
   // Create a new XmlDsigXPathTransform object.
   XmlDsigXPathTransform^ xForm = gcnew XmlDsigXPathTransform;
   
   // Load the XPath XML from the element. 
   xForm->LoadInnerXml( xPathElem->SelectNodes( L"." ) );
   
   // Return the XML that represents the transform.
   return xForm;
}


// Sign an XML file and save the signature in a new file.
static void SignXmlFile( String^ FileName, String^ SignedFileName, RSA^ Key, String^ XPathString )
{
   
   // Create a new XML document.
   XmlDocument^ doc = gcnew XmlDocument;
   
   // Format the document to ignore white spaces.
   doc->PreserveWhitespace = false;
   
   // Load the passed XML file using it's name.
   doc->Load( gcnew XmlTextReader( FileName ) );
   
   // Create a SignedXml object.
   SignedXml^ signedXml = gcnew SignedXml( doc );
   
   // Add the key to the SignedXml document. 
   signedXml->SigningKey = Key;
   
   // Create a reference to be signed.
   Reference^ reference = gcnew Reference;
   reference->Uri = L"";
   
   // Create an XmlDsigXPathTransform object using 
   // the helper method 'CreateXPathTransform' defined
   // later in this sample.
   XmlDsigXPathTransform^ XPathTransform = CreateXPathTransform( XPathString );
   
   // Add the transform to the reference.
   reference->AddTransform( XPathTransform );
   
   // Add the reference to the SignedXml object.
   signedXml->AddReference( reference );
   
   // Add an RSAKeyValue KeyInfo (optional; helps recipient find key to validate).
   KeyInfo^ keyInfo = gcnew KeyInfo;
   keyInfo->AddClause( gcnew RSAKeyValue( dynamic_cast<RSA^>(Key) ) );
   signedXml->KeyInfo = keyInfo;
   
   // Compute the signature.
   signedXml->ComputeSignature();
   
   // Get the XML representation of the signature and save
   // it to an XmlElement object.
   XmlElement^ xmlDigitalSignature = signedXml->GetXml();
   
   // Append the element to the XML document.
   doc->DocumentElement->AppendChild( doc->ImportNode( xmlDigitalSignature, true ) );
   
   // Save the signed XML document to a file specified
   // using the passed string.
   XmlTextWriter^ xmltw = gcnew XmlTextWriter( SignedFileName,gcnew UTF8Encoding( false ) );
   doc->WriteTo( xmltw );
   xmltw->Close();
}


// Verify the signature of an XML file and return the result.
static Boolean VerifyXmlFile( String^ Name )
{
   
   // Create a new XML document.
   XmlDocument^ xmlDocument = gcnew XmlDocument;
   
   // Format using white spaces.
   xmlDocument->PreserveWhitespace = true;
   
   // Load the passed XML file into the document. 
   xmlDocument->Load( Name );
   
   // Create a new SignedXml object and pass it
   // the XML document class.
   SignedXml^ signedXml = gcnew SignedXml( xmlDocument );
   
   // Find the "Signature" node and create a new
   // XmlNodeList object.
   XmlNodeList^ nodeList = xmlDocument->GetElementsByTagName( L"Signature" );
   
   // Load the signature node.
   signedXml->LoadXml( dynamic_cast<XmlElement^>(nodeList->Item( 0 )) );
   
   // Check the signature and return the result.
   return signedXml->CheckSignature();
}


// Create example data to sign.
static void CreateSomeXml( String^ FileName )
{
   
   // Create a new XmlDocument object.
   XmlDocument^ document = gcnew XmlDocument;
   
   // Create a new XmlNode object.
   XmlNode^ node = document->CreateNode( XmlNodeType::Element, L"", L"MyXML", L"Don't_Sign" );
   
   // Append the node to the document.
   document->AppendChild( node );
   
   // Create a new XmlNode object.
   XmlNode^ subnode = document->CreateNode( XmlNodeType::Element, L"", L"TempElement", L"Sign" );
   
   // Add some text to the node.
   subnode->InnerText = L"Here is some data to sign.";
   
   // Append the node to the document.
   document->DocumentElement->AppendChild( subnode );
   
   // Save the XML document to the file name specified.
   XmlTextWriter^ xmltw = gcnew XmlTextWriter( FileName,gcnew UTF8Encoding( false ) );
   document->WriteTo( xmltw );
   xmltw->Close();
}

int main()
{
   
   // Generate a signing key.
   RSA^ Key = RSA::Create();
   try
   {
      
      // Create an XML file to sign.
      CreateSomeXml( L"Example.xml" );
      Console::WriteLine( L"New XML file created." );
      
      // Sign the XML that was just created and save it in a 
      // new file.
      SignXmlFile( L"Example.xml", L"SignedExample.xml", Key, L"ancestor-or-self::TempElement" );
      Console::WriteLine( L"XML file signed." );
      
      // Verify the signature of the signed XML.
      Console::WriteLine( L"Verifying signature..." );
      bool result = VerifyXmlFile( L"SignedExample.xml" );
      
      // Display the results of the signature verification to \
      // the console.
      if ( result )
      {
         Console::WriteLine( L"The XML signature is valid." );
      }
      else
      {
         Console::WriteLine( L"The XML signature is not valid." );
      }
   }
   catch ( CryptographicException^ e ) 
   {
      Console::WriteLine( e->Message );
   }
   finally
   {
      Key->Clear();
   }

   return 1;
}

//
// This example signs an XML file using an
// envelope signature. It then verifies the
// signed XML.
//
using System;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Security.Cryptography.Xml;
using System.Text;
using System.Xml;

public class SignVerifyEnvelope
{

    public static void Main(String[] args)
    {
        // Generate a signing key.
        RSA Key = RSA.Create();

        try
        {
            // Create an XML file to sign.
            CreateSomeXml("Example.xml");
            Console.WriteLine("New XML file created.");

            // Sign the XML that was just created and save it in a
            // new file.
            SignXmlFile("Example.xml", "SignedExample.xml", Key, "ancestor-or-self::TempElement");
            Console.WriteLine("XML file signed.");

            // Verify the signature of the signed XML.
            Console.WriteLine("Verifying signature...");
            bool result = VerifyXmlFile("SignedExample.xml");

            // Display the results of the signature verification to \
            // the console.
            if (result)
            {
                Console.WriteLine("The XML signature is valid.");
            }
            else
            {
                Console.WriteLine("The XML signature is not valid.");
            }
        }
        catch (CryptographicException e)
        {
            Console.WriteLine(e.Message);
        }
        finally
        {
            Key.Clear();
        }
    }

    // Sign an XML file and save the signature in a new file.
    public static void SignXmlFile(string FileName, string SignedFileName, RSA Key, string XPathString)
    {
        // Create a new XML document.
        XmlDocument doc = new XmlDocument();

        // Format the document to ignore white spaces.
        doc.PreserveWhitespace = false;

        // Load the passed XML file using it's name.
        doc.Load(new XmlTextReader(FileName));

        // Create a SignedXml object.
        SignedXml signedXml = new SignedXml(doc);

        // Add the key to the SignedXml document.
        signedXml.SigningKey = Key;

        // Create a reference to be signed.
        Reference reference = new Reference();
        reference.Uri = "";

        // Create an XmlDsigXPathTransform object using
        // the helper method 'CreateXPathTransform' defined
        // later in this sample.

        XmlDsigXPathTransform XPathTransform = CreateXPathTransform(XPathString);

        // Add the transform to the reference.
        reference.AddTransform(XPathTransform);

        // Add the reference to the SignedXml object.
        signedXml.AddReference(reference);

        // Add an RSAKeyValue KeyInfo (optional; helps recipient find key to validate).
        KeyInfo keyInfo = new KeyInfo();
        keyInfo.AddClause(new RSAKeyValue((RSA)Key));
        signedXml.KeyInfo = keyInfo;

        // Compute the signature.
        signedXml.ComputeSignature();

        // Get the XML representation of the signature and save
        // it to an XmlElement object.
        XmlElement xmlDigitalSignature = signedXml.GetXml();

        // Append the element to the XML document.
        doc.DocumentElement.AppendChild(doc.ImportNode(xmlDigitalSignature, true));

        // Save the signed XML document to a file specified
        // using the passed string.
        XmlTextWriter xmltw = new XmlTextWriter(SignedFileName, new UTF8Encoding(false));
        doc.WriteTo(xmltw);
        xmltw.Close();
    }
    // Verify the signature of an XML file and return the result.
    public static Boolean VerifyXmlFile(String Name)
    {
        // Create a new XML document.
        XmlDocument xmlDocument = new XmlDocument();

        // Format using white spaces.
        xmlDocument.PreserveWhitespace = true;

        // Load the passed XML file into the document.
        xmlDocument.Load(Name);

        // Create a new SignedXml object and pass it
        // the XML document class.
        SignedXml signedXml = new SignedXml(xmlDocument);

        // Find the "Signature" node and create a new
        // XmlNodeList object.
        XmlNodeList nodeList = xmlDocument.GetElementsByTagName("Signature");

        // Load the signature node.
        signedXml.LoadXml((XmlElement)nodeList[0]);

        // Check the signature and return the result.
        return signedXml.CheckSignature();
    }

    // Create the XML that represents the transform.
    private static XmlDsigXPathTransform CreateXPathTransform(string XPathString)
    {
        // Create a new XMLDocument object.
        XmlDocument doc = new XmlDocument();

        // Create a new XmlElement.
        XmlElement xPathElem = doc.CreateElement("XPath");

        // Set the element text to the value
        // of the XPath string.
        xPathElem.InnerText = XPathString;

        // Create a new XmlDsigXPathTransform object.
        XmlDsigXPathTransform xForm = new XmlDsigXPathTransform();

        // Load the XPath XML from the element.
        xForm.LoadInnerXml(xPathElem.SelectNodes("."));

        // Return the XML that represents the transform.
        return xForm;
    }

    // Create example data to sign.
    public static void CreateSomeXml(string FileName)
    {
        // Create a new XmlDocument object.
        XmlDocument document = new XmlDocument();

        // Create a new XmlNode object.
        XmlNode node = document.CreateNode(XmlNodeType.Element, "", "MyXML", "Don't_Sign");

        // Append the node to the document.
        document.AppendChild(node);

        // Create a new XmlNode object.
        XmlNode subnode = document.CreateNode(XmlNodeType.Element, "", "TempElement", "Sign");

        // Add some text to the node.
        subnode.InnerText = "Here is some data to sign.";

        // Append the node to the document.
        document.DocumentElement.AppendChild(subnode);

        // Save the XML document to the file name specified.
        XmlTextWriter xmltw = new XmlTextWriter(FileName, new UTF8Encoding(false));
        document.WriteTo(xmltw);
        xmltw.Close();
    }
}

'
' This example signs an XML file using an
' envelope signature. It then verifies the 
' signed XML.
'
Imports System.Security.Cryptography
Imports System.Security.Cryptography.X509Certificates
Imports System.Security.Cryptography.Xml
Imports System.Text
Imports System.Xml



Module SignVerifyEnvelope


    Sub Main(ByVal args() As String)
        ' Generate a signing key.
        Dim Key As RSA = RSA.Create()

        Try
            ' Create an XML file to sign.
            CreateSomeXml("Example.xml")
            Console.WriteLine("New XML file created.")

            ' Sign the XML that was just created and save it in a 
            ' new file.
            SignXmlFile("Example.xml", "SignedExample.xml", Key, "ancestor-or-self::TempElement")
            Console.WriteLine("XML file signed.")

            ' Verify the signature of the signed XML.
            Console.WriteLine("Verifying signature...")
            Dim result As Boolean = VerifyXmlFile("SignedExample.xml")

            ' Display the results of the signature verification to \
            ' the console.
            If result Then
                Console.WriteLine("The XML signature is valid.")
            Else
                Console.WriteLine("The XML signature is not valid.")
            End If
        Catch e As CryptographicException
            Console.WriteLine(e.Message)
        Finally
            Key.Clear()
        End Try

    End Sub


    ' Sign an XML file and save the signature in a new file.
    Sub SignXmlFile(ByVal FileName As String, ByVal SignedFileName As String, ByVal Key As RSA, ByVal XPathString As String)
        ' Create a new XML document.
        Dim doc As New XmlDocument()

        ' Format the document to ignore white spaces.
        doc.PreserveWhitespace = False

        ' Load the passed XML file using it's name.
        doc.Load(New XmlTextReader(FileName))

        ' Create a SignedXml object.
        Dim signedXml As New SignedXml(doc)

        ' Add the key to the SignedXml document. 
        signedXml.SigningKey = Key

        ' Create a reference to be signed.
        Dim reference As New Reference()
        reference.Uri = ""

        ' Create an XmlDsigXPathTransform object using 
        ' the helper method 'CreateXPathTransform' defined
        ' later in this sample.
        Dim XPathTransform As XmlDsigXPathTransform = CreateXPathTransform(XPathString)

        ' Add the transform to the reference.
        reference.AddTransform(XPathTransform)

        ' Add the reference to the SignedXml object.
        signedXml.AddReference(reference)

        ' Add an RSAKeyValue KeyInfo (optional; helps recipient find key to validate).
        Dim keyInfo As New KeyInfo()
        keyInfo.AddClause(New RSAKeyValue(CType(Key, RSA)))
        signedXml.KeyInfo = keyInfo

        ' Compute the signature.
        signedXml.ComputeSignature()

        ' Get the XML representation of the signature and save
        ' it to an XmlElement object.
        Dim xmlDigitalSignature As XmlElement = signedXml.GetXml()

        ' Append the element to the XML document.
        doc.DocumentElement.AppendChild(doc.ImportNode(xmlDigitalSignature, True))

        ' Save the signed XML document to a file specified
        ' using the passed string.
        Dim xmltw As New XmlTextWriter(SignedFileName, New UTF8Encoding(False))
        doc.WriteTo(xmltw)
        xmltw.Close()

    End Sub

    ' Verify the signature of an XML file and return the result.
    Function VerifyXmlFile(ByVal Name As String) As [Boolean]
        ' Create a new XML document.
        Dim xmlDocument As New XmlDocument()

        ' Format using white spaces.
        xmlDocument.PreserveWhitespace = True

        ' Load the passed XML file into the document. 
        xmlDocument.Load(Name)

        ' Create a new SignedXml object and pass it
        ' the XML document class.
        Dim signedXml As New SignedXml(xmlDocument)

        ' Find the "Signature" node and create a new
        ' XmlNodeList object.
        Dim nodeList As XmlNodeList = xmlDocument.GetElementsByTagName("Signature")

        ' Load the signature node.
        signedXml.LoadXml(CType(nodeList(0), XmlElement))

        ' Check the signature and return the result.
        Return signedXml.CheckSignature()

    End Function


    ' Create the XML that represents the transform.
    Function CreateXPathTransform(ByVal XPathString As String) As XmlDsigXPathTransform
        ' Create a new XMLDocument object.
        Dim doc As New XmlDocument()

        ' Create a new XmlElement.
        Dim xPathElem As XmlElement = doc.CreateElement("XPath")

        ' Set the element text to the value
        ' of the XPath string.
        xPathElem.InnerText = XPathString

        ' Create a new XmlDsigXPathTransform object.
        Dim xForm As New XmlDsigXPathTransform()

        ' Load the XPath XML from the element. 
        xForm.LoadInnerXml(xPathElem.SelectNodes("."))

        ' Return the XML that represents the transform.
        Return xForm

    End Function


    ' Create example data to sign.
    Sub CreateSomeXml(ByVal FileName As String)
        ' Create a new XmlDocument object.
        Dim document As New XmlDocument()

        ' Create a new XmlNode object.
        Dim node As XmlNode = document.CreateNode(XmlNodeType.Element, "", "MyXML", "Don't_Sign")

        ' Append the node to the document.
        document.AppendChild(node)

        ' Create a new XmlNode object.
        Dim subnode As XmlNode = document.CreateNode(XmlNodeType.Element, "", "TempElement", "Sign")

        ' Add some text to the node.
        subnode.InnerText = "Here is some data to sign."

        ' Append the node to the document.
        document.DocumentElement.AppendChild(subnode)

        ' Save the XML document to the file name specified.
        Dim xmltw As New XmlTextWriter(FileName, New UTF8Encoding(False))
        document.WriteTo(xmltw)
        xmltw.Close()

    End Sub
End Module

Ejemplo 2

using System;
using System.IO;
using System.Xml;
using System.Security.Cryptography;
using System.Security.Cryptography.Xml;

class Class1
{
    [STAThread]
    static void Main(string[] args)
    {
        // Encrypt a sample XML string.
        XmlDocument productsXml = LoadProducts();
        ShowTransformProperties(productsXml);

        // Encrypt an XPath Xml string.
        XmlDocument transformXml = LoadTransformByXml();
        ShowTransformProperties(transformXml);

        // Use XmlDsigXPathTransform to resolve a Uri.
        Uri baseUri = new Uri("http://www.contoso.com");
        string relativeUri = "xml";
        Uri absoluteUri = ResolveUris(baseUri, relativeUri);

        Console.WriteLine("This sample completed successfully; " +
            "press Enter to exit.");
        Console.ReadLine();
    }

    // Encrypt the text in the specified XmlDocument.
    private static void ShowTransformProperties(XmlDocument xmlDoc)
    {

        // Create a new XMLDocument object.
        XmlDocument doc = new XmlDocument();

        // Create a new XmlElement.
        XmlElement xPathElem = doc.CreateElement("XPath");

        // Set the element text to the value
        // of the XPath string.
        xPathElem.InnerText = "ancestor-or-self::PRODUCTS";

        // Create a new XmlDsigXPathTransform object.
        XmlDsigXPathTransform xmlTransform = new XmlDsigXPathTransform();

        // Load the XPath XML from the element. 
        xmlTransform.LoadInnerXml(xPathElem.SelectNodes("."));

        // Ensure the transform is using the proper algorithm.
        xmlTransform.Algorithm =
            SignedXml.XmlDsigXPathTransformUrl;

        // Retrieve the XML representation of the current transform.
        XmlElement xmlInTransform = xmlTransform.GetXml();

        Console.WriteLine("\nXml representation of the current transform: ");
        Console.WriteLine(xmlInTransform.OuterXml);

        // Retrieve the valid input types for the current transform.
        Type[] validInTypes = xmlTransform.InputTypes;

        // Verify the xmlTransform can accept the XMLDocument as an
        // input type.
        for (int i = 0; i < validInTypes.Length; i++)
        {
            if (validInTypes[i] == xmlDoc.GetType())
            {
                // Load the document into the transfrom.
                xmlTransform.LoadInput(xmlDoc);

                try
                {
                    // This transform is created for demonstration purposes.
                    XmlDsigXPathTransform secondTransform =
                        new XmlDsigXPathTransform();

                    string classDescription = secondTransform.ToString();

                    xmlTransform.LoadInnerXml(xPathElem.SelectNodes(".")); ;
                }
                catch (CryptographicException)
                {
                    Console.WriteLine("Caught exception while trying to " +
                        "load the specified Xml document. The document " +
                        "requires an XPath element to be valid.");
                }
                break;
            }
        }

        Type[] validOutTypes = xmlTransform.OutputTypes;

        for (int i = validOutTypes.Length - 1; i >= 0; i--)
        {
            if (validOutTypes[i] == typeof(System.Xml.XmlDocument))
            {
                try
                {
                    Type xmlDocumentType = typeof(System.Xml.XmlDocument);
                    XmlDocument xmlDocumentOutput = (XmlDocument)
                        xmlTransform.GetOutput(xmlDocumentType);

                    // Display to the console the Xml before and after
                    // encryption.
                    Console.WriteLine("Result of the GetOutput method call" +
                        " from the current transform: " +
                        xmlDocumentOutput.OuterXml);
                }
                catch (Exception ex)
                {
                    Console.WriteLine("Unexpected exception caught: " +
                        ex.ToString());
                }

                break;
            }
            else if (validOutTypes[i] == typeof(System.Xml.XmlNodeList))
            {
                try
                {
                    Type xmlNodeListType = typeof(System.Xml.XmlNodeList);
                    XmlNodeList xmlNodes = (XmlNodeList)
                        xmlTransform.GetOutput(xmlNodeListType);

                    // Display to the console the Xml before and after
                    // encryption.
                    Console.WriteLine("Encoding the following message: " +
                        xmlDoc.InnerText);

                    Console.WriteLine("Nodes of the XmlNodeList retrieved " +
                        "from GetOutput:");
                    for (int j = 0; j < xmlNodes.Count; j++)
                    {
                        Console.WriteLine("Node " + j +
                            " has the following name: " +
                            xmlNodes.Item(j).Name +
                            " and the following InnerXml: " +
                            xmlNodes.Item(j).InnerXml);
                    }
                }
                catch (Exception ex)
                {
                    Console.WriteLine("Unexpected exception caught: " +
                        ex.ToString());
                }

                break;
            }
            else
            {
                object outputObject = xmlTransform.GetOutput();
            }
        }
    }

    // Create an XML document for the dsig namespace.
    private static XmlDocument LoadTransformByXml()
    {
        XmlDocument xmlDoc = new XmlDocument();

        string transformXml = "<Signature><Reference URI=''><Transforms>";
        transformXml += "<Transform><XPath ";
        transformXml += "xmlns:dsig='http://www.w3.org/2000/09/xmldsig#'>";
        transformXml += "not(ancestor-or-self::dsig:Signature)";
        transformXml += "</XPath></Transform>";
        transformXml += "</Transforms></Reference></Signature>";

        xmlDoc.LoadXml(transformXml);
        return xmlDoc;
    }

    // Create an XML document describing various products.
    private static XmlDocument LoadProducts()
    {
        XmlDocument xmlDoc = new XmlDocument();

        string contosoProducts = "<PRODUCTS>";
        contosoProducts += "<PRODUCT><ID>123</ID>";
        contosoProducts += "<DESCRIPTION>Router</DESCRIPTION></PRODUCT>";
        contosoProducts += "<PRODUCT><ID>456</ID>";
        contosoProducts += "<DESCRIPTION>Keyboard</DESCRIPTION></PRODUCT>";
        contosoProducts += "<PRODUCT><ID>789</ID>";
        contosoProducts += "<DESCRIPTION>Monitor</DESCRIPTION></PRODUCT>";
        contosoProducts += "</PRODUCTS>";

        xmlDoc.LoadXml(contosoProducts);
        return xmlDoc;
    }

    // Resolve the specified base and relative Uri's .
    private static Uri ResolveUris(Uri baseUri, string relativeUri)
    {
        XmlUrlResolver xmlResolver = new XmlUrlResolver();
        xmlResolver.Credentials =
            System.Net.CredentialCache.DefaultCredentials;

        XmlDsigXPathTransform xmlTransform =
            new XmlDsigXPathTransform();
        xmlTransform.Resolver = xmlResolver;

        Uri absoluteUri = xmlResolver.ResolveUri(baseUri, relativeUri);

        if (absoluteUri != null)
        {
            Console.WriteLine(
                "\nResolved the base Uri and relative Uri to the following:");
            Console.WriteLine(absoluteUri.ToString());
        }
        else
        {
            Console.WriteLine(
                "Unable to resolve the base Uri and relative Uri");
        }
        return absoluteUri;
    }
}

Imports System.IO
Imports System.Xml
Imports System.Security.Cryptography
Imports System.Security.Cryptography.Xml



Class Class1

    <STAThread()> _
    Shared Sub Main(ByVal args() As String)
        ' Encrypt a sample XML string.
        Dim productsXml As XmlDocument = LoadProducts()
        ShowTransformProperties(productsXml)

        ' Encrypt an XPath Xml string.
        Dim transformXml As XmlDocument = LoadTransformByXml()
        ShowTransformProperties(transformXml)

        ' Use XmlDsigXPathTransform to resolve a Uri.
        Dim baseUri As New Uri("http://www.contoso.com")
        Dim relativeUri As String = "xml"
        Dim absoluteUri As Uri = ResolveUris(baseUri, relativeUri)

        Console.WriteLine("This sample completed successfully; " + "press Enter to exit.")
        Console.ReadLine()

    End Sub


    ' Encrypt the text in the specified XmlDocument.
    Private Shared Sub ShowTransformProperties(ByVal xmlDoc As XmlDocument)
        ' Create a new XMLDocument object.
        Dim doc As New XmlDocument()

        ' Create a new XmlElement.
        Dim xPathElem As XmlElement = doc.CreateElement("XPath")

        ' Set the element text to the value
        ' of the XPath string.
        xPathElem.InnerText = "ancestor-or-self::PRODUCTS"

        ' Create a new XmlDsigXPathTransform object.
        Dim xmlTransform As New XmlDsigXPathTransform()

        ' Load the XPath XML from the element. 
        xmlTransform.LoadInnerXml(xPathElem.SelectNodes("."))
        ' Ensure the transform is using the proper algorithm.
        xmlTransform.Algorithm = SignedXml.XmlDsigXPathTransformUrl
        ' Retrieve the XML representation of the current transform.
        Dim xmlInTransform As XmlElement = xmlTransform.GetXml()
        Console.WriteLine(vbLf + "Xml representation of the current transform: ")
        Console.WriteLine(xmlInTransform.OuterXml)

        ' Retrieve the valid input types for the current transform.
        Dim validInTypes As Type() = xmlTransform.InputTypes
        ' Verify the xmlTransform can accept the XMLDocument as an
        ' input type.
        Dim i As Integer
        For i = 0 To validInTypes.Length
            If validInTypes(i).Equals(xmlDoc.GetType()) Then
                ' Load the document into the transfrom.
                xmlTransform.LoadInput(xmlDoc)
                Try
                    ' This transform is created for demonstration purposes.
                    Dim secondTransform As New XmlDsigXPathTransform()

                    Dim classDescription As String = secondTransform.ToString()
                    xmlTransform.LoadInnerXml(xPathElem.SelectNodes("."))
                Catch
                    Console.WriteLine("Caught exception while trying to " + "load the specified Xml document. The document " + "requires an XPath element to be valid.")
                End Try
                Exit For
            End If
        Next i

        Dim validOutTypes As Type() = xmlTransform.OutputTypes
        For i = validOutTypes.Length - 1 To 0 Step -1
            If validOutTypes(i).Equals(GetType(System.Xml.XmlDocument)) Then
                Try
                    Dim xmlDocumentType As Type = GetType(System.Xml.XmlDocument)
                    Dim xmlDocumentOutput As XmlDocument = CType(xmlTransform.GetOutput(xmlDocumentType), XmlDocument)
                    ' Display to the console the Xml before and after
                    ' encryption.
                    Console.WriteLine("Result of the GetOutput method call" + " from the current transform: " + xmlDocumentOutput.OuterXml)
                Catch ex As Exception
                    Console.WriteLine("Unexpected exception caught: " + ex.ToString())
                End Try

                Exit For
            ElseIf validOutTypes(i).Equals(GetType(System.Xml.XmlNodeList)) Then
                Try
                    Dim xmlNodeListType As Type = GetType(System.Xml.XmlNodeList)
                    Dim xmlNodes As XmlNodeList = CType(xmlTransform.GetOutput(xmlNodeListType), XmlNodeList)

                    ' Display to the console the Xml before and after
                    ' encryption.
                    Console.WriteLine("Encoding the following message: " + xmlDoc.InnerText)

                    Console.WriteLine("Nodes of the XmlNodeList retrieved " + "from GetOutput:")
                    For j As Integer = 0 To xmlNodes.Count - 1
                        Console.WriteLine("Node " + j + " has the following name: " + xmlNodes.Item(j).Name + " and the following InnerXml: " + xmlNodes.Item(j).InnerXml)
                    Next
                Catch ex As Exception
                    Console.WriteLine("Unexpected exception caught: " + ex.ToString())
                End Try

                Exit For
            Else
                Dim outputObject As Object = xmlTransform.GetOutput()
            End If 
        Next i

    End Sub


    ' Create an XML document for the dsig namespace.
    Private Shared Function LoadTransformByXml() As XmlDocument
        Dim xmlDoc As New XmlDocument()

        Dim transformXml As String = "<Signature><Reference URI=''><Transforms>"
        transformXml += "<Transform><XPath "
        transformXml += "xmlns:dsig='http://www.w3.org/2000/09/xmldsig#'>"
        transformXml += "not(ancestor-or-self::dsig:Signature)"
        transformXml += "</XPath></Transform>"
        transformXml += "</Transforms></Reference></Signature>"

        xmlDoc.LoadXml(transformXml)
        Return xmlDoc

    End Function 'LoadTransformByXml


    ' Create an XML document describing various products.
    Private Shared Function LoadProducts() As XmlDocument
        Dim xmlDoc As New XmlDocument()

        Dim contosoProducts As String = "<PRODUCTS>"
        contosoProducts += "<PRODUCT><ID>123</ID>"
        contosoProducts += "<DESCRIPTION>Router</DESCRIPTION></PRODUCT>"
        contosoProducts += "<PRODUCT><ID>456</ID>"
        contosoProducts += "<DESCRIPTION>Keyboard</DESCRIPTION></PRODUCT>"
        contosoProducts += "<PRODUCT><ID>789</ID>"
        contosoProducts += "<DESCRIPTION>Monitor</DESCRIPTION></PRODUCT>"
        contosoProducts += "</PRODUCTS>"

        xmlDoc.LoadXml(contosoProducts)
        Return xmlDoc

    End Function 'LoadProducts


    ' Resolve the specified base and relative Uri's .
    Private Shared Function ResolveUris(ByVal baseUri As Uri, ByVal relativeUri As String) As Uri
        Dim xmlResolver As New XmlUrlResolver()
        xmlResolver.Credentials = System.Net.CredentialCache.DefaultCredentials

        Dim xmlTransform As New XmlDsigXPathTransform()
        xmlTransform.Resolver = xmlResolver
        Dim absoluteUri As Uri = xmlResolver.ResolveUri(baseUri, relativeUri)

        If Not (absoluteUri Is Nothing) Then
            Console.WriteLine(vbLf + "Resolved the base Uri and relative Uri to the following:")
            Console.WriteLine(absoluteUri.ToString())
        Else
            Console.WriteLine("Unable to resolve the base Uri and relative Uri")
        End If
        Return absoluteUri

    End Function
End Class

Comentarios

La XmlDsigXPathTransform clase permite dirigir un documento XML mediante el lenguaje XPath. Esta clase usa una expresión XPath para seleccionar los nodos XML que desea firmar o cifrar al quitar todos los demás de cualquiera de las operaciones criptográficas.

Use la XmlDsigXPathTransform clase para firmar o cifrar partes específicas de un documento XML mediante una expresión XPath. Para obtener información sobre cómo inicializar la XmlDsigXPathTransform clase en el valor de una cadena de transformación XPath, vea el LoadInnerXml método .

El identificador uniforme de recursos (URI) que describe la XmlDsigXPathTransform clase se define mediante el XmlDsigXPathTransformUrl campo .

Para obtener más información sobre la transformación XPath, vea la sección 6.6.3 de la especificación XMLDSIG de W3C.

Constructores

XmlDsigXPathTransform()

Inicializa una nueva instancia de la clase XmlDsigXPathTransform.

Propiedades

Algorithm	Obtiene o establece el identificador uniforme de recursos (URI) que identifica el algoritmo ejecutado en la transformación actual. (Heredado de Transform)
Context	Obtiene o establece un objeto XmlElement que representa el contexto del documento en el que se está ejecutando el objeto Transform actual. (Heredado de Transform)
InputTypes	Obtiene una matriz de tipos que son entradas válidas al método LoadInput(Object) del objeto XmlDsigXPathTransform actual.
OutputTypes	Obtiene una matriz de tipos que son posibles resultados de los métodos GetOutput() del objeto XmlDsigXPathTransform actual.
PropagatedNamespaces	Obtiene o establece un objeto Hashtable que contiene los espacios de nombres que se propagan en la firma. (Heredado de Transform)
Resolver	Establece el objeto XmlResolver actual. (Heredado de Transform)

Métodos

Equals(Object)	Determina si el objeto especificado es igual que el objeto actual. (Heredado de Object)
GetDigestedOutput(HashAlgorithm)	Cuando se reemplaza en una clase derivada, devuelve el algoritmo de síntesis asociado a un objeto Transform. (Heredado de Transform)
GetHashCode()	Sirve como la función hash predeterminada. (Heredado de Object)
GetInnerXml()	Devuelve una representación XML de los parámetros de un objeto XmlDsigXPathTransform que son adecuados para incluirlos como subelementos de un elemento <Transform> XMLDSIG.
GetOutput()	Devuelve la salida del objeto XmlDsigXPathTransform actual.
GetOutput(Type)	Devuelve la salida del objeto XmlDsigXPathTransform actual del tipo XmlNodeList.
GetType()	Obtiene el Type de la instancia actual. (Heredado de Object)
GetXml()	Devuelve la representación XML del objeto Transform actual. (Heredado de Transform)
LoadInnerXml(XmlNodeList)	Analiza el objeto XmlNodeList especificado como contenido específico de la transformación de un elemento <Transform> y configura el estado interno del objeto XmlDsigXPathTransform actual para que coincida con el elemento <Transform>.
LoadInput(Object)	Carga la entrada especificada en el objeto XmlDsigXPathTransform actual.
MemberwiseClone()	Crea una copia superficial del Object actual. (Heredado de Object)
ToString()	Devuelve una cadena que representa el objeto actual. (Heredado de Object)