SignedXml.XmlDsigExcC14NWithCommentsTransformUrl Field


Represents the Uniform Resource Identifier (URI) for exclusive XML canonicalization, with comments. This field is constant.

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

public const string XmlDsigExcC14NWithCommentsTransformUrl

Field Value

Type: System.String

The value of the XmlDsigExcC14NWithCommentsTransformUrl field is "".

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

The XmlDsigExcC14NWithCommentsTransform class implements the transform described by the XmlDsigExcC14NWithCommentsTransformUrl field.

For more information, see the World Wide Web Consortium (W3C) specification at

The following code example shows how to sign and verify an XML document using the XmlDsigExcC14NWithCommentsTransform class. This sample creates an envelope signature.

// 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.
            RSACryptoServiceProvider Key = new RSACryptoServiceProvider();

            // Create an XML file to sign.
            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);
            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.");
                Console.WriteLine("The XML signature is not valid.");
        catch (CryptographicException e)

    // Sign an XML file and save the signature in a new file.
    public static void SignXmlFile(string FileName, string SignedFileName, RSA Key)
        // 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;

        // Specify a canonicalization method.
        signedXml.SignedInfo.CanonicalizationMethod = SignedXml.XmlDsigExcC14NWithCommentsTransformUrl;

        // Set the InclusiveNamespacesPrefixList property.
        XmlDsigExcC14NWithCommentsTransform canMethod = (XmlDsigExcC14NWithCommentsTransform)signedXml.SignedInfo.CanonicalizationMethodObject;
        canMethod.InclusiveNamespacesPrefixList = "Sign";

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

        // Add an enveloped transformation to the reference.
        XmlDsigEnvelopedSignatureTransform env = new XmlDsigEnvelopedSignatureTransform();

        // Add the reference to the SignedXml object.

        // 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.

        // 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));

        if (doc.FirstChild is XmlDeclaration)

        // Save the signed XML document to a file specified
        // using the passed string.
        XmlTextWriter xmltw = new XmlTextWriter(SignedFileName, new UTF8Encoding(false));
    // 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. 

        // 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.

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


    // 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.

        // 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.

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

.NET Framework
Available since 2.0
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