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XmlDsigXPathTransform Class

Represents the XPath transform for a digital signature as defined by the W3C.

System::Object
  System.Security.Cryptography.Xml::Transform
    System.Security.Cryptography.Xml::XmlDsigXPathTransform

Namespace:  System.Security.Cryptography.Xml
Assembly:  System.Security (in System.Security.dll)

[HostProtectionAttribute(SecurityAction::LinkDemand, MayLeakOnAbort = true)]
public ref class XmlDsigXPathTransform : public Transform

The XmlDsigXPathTransform type exposes the following members.

  NameDescription
Public methodXmlDsigXPathTransformInitializes a new instance of the XmlDsigXPathTransform class.
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  NameDescription
Public propertyAlgorithmGets or sets the Uniform Resource Identifier (URI) that identifies the algorithm performed by the current transform. (Inherited from Transform.)
Public propertyContextGets or sets an XmlElement object that represents the document context under which the current Transform object is running. (Inherited from Transform.)
Public propertyInputTypesGets an array of types that are valid inputs to the LoadInput method of the current XmlDsigXPathTransform object. (Overrides Transform::InputTypes.)
Public propertyOutputTypesGets an array of types that are possible outputs from the GetOutput methods of the current XmlDsigXPathTransform object. (Overrides Transform::OutputTypes.)
Public propertyPropagatedNamespacesGets or sets a Hashtable object that contains the namespaces that are propagated into the signature. (Inherited from Transform.)
Public propertyResolverSets the current XmlResolver object. (Inherited from Transform.)
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  NameDescription
Public methodEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetDigestedOutputWhen overridden in a derived class, returns the digest associated with a Transform object. (Inherited from Transform.)
Public methodGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Protected methodGetInnerXmlReturns an XML representation of the parameters of a XmlDsigXPathTransform object that are suitable to be included as subelements of an XMLDSIG <Transform> element. (Overrides Transform::GetInnerXml().)
Public methodGetOutput()Returns the output of the current XmlDsigXPathTransform object. (Overrides Transform::GetOutput().)
Public methodGetOutput(Type)Returns the output of the current XmlDsigXPathTransform object of type XmlNodeList. (Overrides Transform::GetOutput(Type).)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodGetXmlReturns the XML representation of the current Transform object. (Inherited from Transform.)
Public methodLoadInnerXmlParses the specified XmlNodeList object as transform-specific content of a <Transform> element and configures the internal state of the current XmlDsigXPathTransform object to match the <Transform> element. (Overrides Transform::LoadInnerXml(XmlNodeList).)
Public methodLoadInputLoads the specified input into the current XmlDsigXPathTransform object. (Overrides Transform::LoadInput(Object).)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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The XmlDsigXPathTransform class allows you to address an XML document using the XPath language. This class uses an XPath expression to select the XML nodes you want to sign or encrypt while removing all others from either cryptographic operation.

Use the XmlDsigXPathTransform class to sign or encrypt specific parts of an XML document using an XPath expression. For information on initializing the XmlDsigXPathTransform class to the value of an XPath transform string, see the LoadInnerXml method.

The Uniform Resource Identifier (URI) that describes the XmlDsigXPathTransform class is defined by the XmlDsigXPathTransformUrl field.

For more information about the XPath transform, see Section 6.6.3 of the XMLDSIG specification, which is available from the W3C at www.w3.org/TR/xmldsig-core/.

NoteNote

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: MayLeakOnAbort. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

This section contains two code examples. The first code example shows how to sign and verify an XML document using the XmlDsigXPathTransform class with an envelope signature. This example signs an XML document and saves the signature in a new XML document. The second code example demonstrates how to call members of the XmlDsigXPathTransform class.

Example #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.
   RSACryptoServiceProvider^ Key = gcnew RSACryptoServiceProvider;
   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;
}



Example #2

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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