Export (0) Print
Expand All

SignedXml.XmlDsigXPathTransformUrl Field

Represents the Uniform Resource Identifier (URI) for the XML Path Language (XPath). This field is constant.

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

public const string XmlDsigXPathTransformUrl

The value of the XmlDsigXPathTransformUrl field is "http://www.w3.org/TR/1999/REC-xpath-19991116".

Use this field to conveniently supply a value to one of the URI attributes of an element used for XMLDSIG.

The XmlDsigXPathTransform class implements the transform described by the XmlDsigXPathTransformUrl field.

For more information, see the World Wide Web Consortium (W3C) specification at http://www.w3.org/TR/1999/REC-xpath-19991116.

The following code example demonstrates how to call members of the XmlDsigXPathTransform class.

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;
    }
}

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

Show:
© 2014 Microsoft