SignedXml.AddObject Method (DataObject)


Adds a DataObject object to the list of objects to be signed.

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

public void AddObject(
	DataObject dataObject


Type: System.Security.Cryptography.Xml.DataObject

The DataObject object to add to the list of objects to be signed.

The AddObject method adds an <Object> element that represents an object to be signed to the <Signature> element of an XML digital signature.

The AddObject method internally calls the AddObject method of the Signature object encapsulated by the SignedXml object. You can also add a DataObject object by directly calling the AddObject method from the Signature property.

For more information about XML digital signatures, see the XMLDSIG specification available at

The following code example computes and XML signature.

using System;
using System.IO;
using System.Security.Cryptography;
using System.Security.Cryptography.Xml;
using System.Xml;

public class XMLdsigsample1 

    static void Main(String[] args)
            // Create example data to sign.
            XmlDocument document = new XmlDocument();
            XmlNode node = document.CreateNode(XmlNodeType.Element, "", "MyElement", "samples");
            node.InnerText = "This is some text";
            Console.WriteLine("Data to sign:\n" + document.OuterXml + "\n");

            // Create the SignedXml message.
            SignedXml signedXml = new SignedXml();
            RSA key = RSA.Create();
            signedXml.SigningKey = key;

            // Create a data object to hold the data to sign.
            DataObject dataObject = new DataObject();
            dataObject.Data = document.ChildNodes;
            dataObject.Id = "MyObjectId";

            // Add the data object to the signature.

            // Create a reference to be able to package everything into the
            // message.
            Reference reference = new Reference();
            reference.Uri = "#MyObjectId";

            // Add the reference to the message.

            // Add a KeyInfo.
            KeyInfo keyInfo = new KeyInfo();
            keyInfo.AddClause(new RSAKeyValue(key));
            signedXml.KeyInfo = keyInfo;

            // Compute the signature.

            Console.WriteLine("The data was signed.");
        catch(CryptographicException e)

.NET Framework
Available since 1.1
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