// -------------------- IterateSignatureDefinitions --------------------
/// <summary>
///   Interates through the SignatureDefinition contained in a given
///   XPS document displaying and updating the signature properties
///   through a user dialog.</summary>
/// <param name="signatureDialog">
///   The user dialog to use in displaying and
///   updating the signature information.</param>
/// <param name="xpsDocument">
///   The XPS document containing the signature information.</param>
public void IterateSignatureDefinitions(
    SignatureDialog signatureDialog, XpsDocument xpsDocument )
{
    IXpsFixedDocumentSequenceReader docSeq =
        xpsDocument.FixedDocumentSequenceReader;

    // For every FixedDocument in the XPS document.
    foreach (IXpsFixedDocumentReader doc in docSeq.FixedDocuments)
    {
        // For every SignatureDefinition in each FixedDocument.
        foreach (XpsSignatureDefinition signature in
                 doc.SignatureDefinitions)
        {
            SignatureDisplayItem item =
                signatureDialog.AddSignatureItem(signature);

            // Signatures are bound to signature definitions by GUID.
            // If the SignatureDefintion SpotId is the same as the
            // SignatureId, the signature is signing that definition.

            // For every signature in the XPS document.
            foreach (XpsDigitalSignature sig in xpsDocument.Signatures)
            {
                if (sig.Id != null && sig.Id == signature.SpotId)
                {
                    X509Certificate2 cert =
                        sig.SignerCertificate as X509Certificate2;
                    item.Signer =
                        cert.GetNameInfo(X509NameType.SimpleName, false);
                    item.IsSigned = true;
                }
            }// end:foreach (XpsDigitalSignature
        }// end:foreach (XpsSignatureDefinition
    }// end:foreach (IXpsFixedDocumentReader
}// end:IterateSignatureDefinitions()