关于 c#:SignedXml 生成无效签名

public static XDocument SignDocument(XDocument originalDocument, X509Certificate2 certificate)
{
    var document = new XmlDocument();
    document.LoadXml(originalDocument.ToString(SaveOptions.DisableFormatting));
    if (document.DocumentElement == null)
        throw new InvalidOperationException("Invalid XML document; no root element found.");

    var signedDocument = new SignedXml(document);
    Reference signatureReference = GetSignatureReference();
    KeyInfo certificateKeyInfo = GetCertificateKeyInfo(certificate);
    var dataObject = new DataObject("","text/xml","utf-8", document.DocumentElement);

    signedDocument.AddReference(signatureReference);
    signedDocument.AddObject(dataObject);
    signedDocument.SigningKey = certificate.PrivateKey;
    signedDocument.KeyInfo = certificateKeyInfo;
    signedDocument.ComputeSignature();

    return XDocument.Parse(signedDocument.GetXml().OuterXml, LoadOptions.PreserveWhitespace);
}

private static Reference GetSignatureReference()
{
    var signatureReference = new Reference("");
    signatureReference.AddTransform(new XmlDsigEnvelopedSignatureTransform());

    return signatureReference;
}

private static KeyInfo GetCertificateKeyInfo(X509Certificate certificate)
{
    var certificateKeyInfo = new KeyInfo();
    certificateKeyInfo.AddClause(new KeyInfoX509Data(certificate));

    return certificateKeyInfo;
}