XmlDsigBase64Transform Class

Represents the Base64 decoding transform as defined in Section 6.6.2 of the XMLDSIG specification.

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

public class XmlDsigBase64Transform : Transform

Use the XmlDsigBase64Transform object when you need to sign the raw data associated with the encoded content of an element.

The Uniform Resource Identifier (URI) that describes the XmlDsigBase64Transform object is defined by the XmlDsigBase64TransformUrl field.

For more information about the Base64 decoding transform, see Section 6.6.2 of the XMLDSIG specification, which is available from the W3C at www.w3.org/TR/xmldsig-core/.

The following code example demonstrates how to use members of the XmlDsigBase64Transform 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 an XML message
        EncryptXML(LoadXMLDoc());

        // Using XmlDsigBase64Transform resolving a Uri.
        Uri baseUri = new Uri("http://www.microsoft.com");
        string relativeUri = "msdn";
        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 EncryptXML(XmlDocument xmlDoc)
    {
        XmlDsigBase64Transform xmlTransform = new XmlDsigBase64Transform();

        // Ensure the transform is using the proper algorithm.
        xmlTransform.Algorithm = SignedXml.XmlDsigBase64TransformUrl;

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

        Console.WriteLine("Xml 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())
            {
                // Demonstrate loading the entire Xml Document.
                xmlTransform.LoadInput(xmlDoc);

                // This transform is created for demonstration purposes.
                XmlDsigBase64Transform secondTransform =
                    new XmlDsigBase64Transform();

                string classDescription = secondTransform.ToString();

                // This call does not perform as expected. 
                // LoadInnerXml is overridden by the XmlDsigBase64Transform 
                // class, but is stubbed out.
                secondTransform.LoadInnerXml(xmlDoc.SelectNodes("//."));

                break;
            }
        }

        Type[] validOutTypes = xmlTransform.OutputTypes;

        for (int i=0; i<validOutTypes.Length; i++)
        {
            if (validOutTypes[i] == typeof(System.IO.Stream))
            {
                try 
                {
                    Type streamType = typeof(System.IO.Stream);
                    CryptoStream outputStream = (CryptoStream) 
                        xmlTransform.GetOutput(streamType);

                    // Read the CryptoStream into a stream reader.
                    StreamReader streamReader =
                        new StreamReader(outputStream);

                    // Read the stream into a string.
                    string outputMessage = streamReader.ReadToEnd();

                    // Close the streams.
                    outputStream.Close();
                    streamReader.Close();

                    // Display to the console the Xml before and after 
                    // encryption.
                    Console.WriteLine("Encoding the following message: " +
                        xmlDoc.InnerText);
                    Console.WriteLine("Message encoded: " + outputMessage);
            }
                catch (Exception ex)
                {
                    Console.WriteLine("Unexpected exception caught: " +
                        ex.ToString());
                }

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

    // Create an XML document with Element and Text nodes. 
    private static XmlDocument LoadXMLDoc()
    {
        XmlDocument xmlDoc = new XmlDocument();

        XmlNode mainNode = xmlDoc.CreateNode(
            XmlNodeType.Element,
            "ContosoMessages",
            "http://www.contoso.com");

        XmlNode textNode = xmlDoc.CreateTextNode("Some text to encode.");
        mainNode.AppendChild(textNode);
        xmlDoc.AppendChild(mainNode);

        Console.WriteLine("Created the following XML Document for " +
            "transformation: ");
        Console.WriteLine(xmlDoc.InnerXml);
        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;

        XmlDsigBase64Transform xmlTransform = new XmlDsigBase64Transform();
        xmlTransform.Resolver = xmlResolver;

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

        if (absoluteUri != null)
        {
            Console.WriteLine(
                "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");
        }
        return absoluteUri;
    }
}
// 
// This sample produces the following output: 
// 
// Created the following XML Document for transformation: 
// <ContosoMessages xmlns="http://www.contoso.com">Some text to encode.
// </ContosoMessages> 
// Xml representation of the current transform: 
// <Transform Algorithm="http://www.w3.org/2000/09/xmldsig#base64" xmlns=
// "http://www.w3.org/2000/09/xmldsig#" />
// Encoding the following message: Some text to encode. 
// Message encoded: Jmr^ 
// Resolved the base Uri and relative Uri to the following: 
// http://www.microsoft.com/msdn 
// This sample completed successfully; press Enter to exit.

System.Object
  System.Security.Cryptography.Xml.Transform
    System.Security.Cryptography.Xml.XmlDsigBase64Transform

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

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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

.NET Framework

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