Reference Class


Represents the <reference> element of an XML signature.

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


[HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort = true)]
public class Reference


Initializes a new instance of the Reference class with default properties.


Initializes a new instance of the Reference class with a hash value of the specified Stream.


Initializes a new instance of the Reference class with the specified Uri.


Gets or sets the digest method Uniform Resource Identifier (URI) of the current Reference.


Gets or sets the digest value of the current Reference.


Gets or sets the ID of the current Reference.


Gets the transform chain of the current Reference.


Gets or sets the type of the object being signed.


Gets or sets the Uri of the current Reference.


Adds a Transform object to the list of transforms to be performed on the data before passing it to the digest algorithm.


Determines whether the specified object is equal to the current object.(Inherited from Object.)


Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)


Serves as the default hash function. (Inherited from Object.)


Gets the Type of the current instance.(Inherited from Object.)


Returns the XML representation of the Reference.


Loads a Reference state from an XML element.


Creates a shallow copy of the current Object.(Inherited from Object.)


Returns a string that represents the current object.(Inherited from Object.)

The Reference object represents the <reference> element of an XML digital signature defined by the XML digital signature specification.

Use the Reference object to specify the following information:

  • The digest algorithm used to sign of the data object. This value is required.

  • The Uniform Resource Identifier (URI) of the data object to sign. The URI can specify a file path or specific elements within an XML document. This value is required.

  • A chain of transforms to apply before generating the digest. This value is optional.

  • The type of object to sign. This value is optional.

  • A unique identifier used to reference the current <reference> element. This value is optional.

For more information about the <reference> element, see the W3C specification at

The following code example demonstrates how to generate and verify an enveloped XML signature using the Reference object.

// 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.
                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;

        // 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, "", "MyElement", "samples");

        // Add some text to the node.
        node.InnerText = "Example text to be signed.";

        // 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 1.1

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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