C# 如何读取X509证书并将其附加到Xml数字签名？

我想从TrustedPeople存储中读取x509证书，并将其附加到XML文档中

            RSAKeyValue rsaKey = new RSAKeyValue();
            XmlDocument xmlDoc = new XmlDocument();
            string filename = "C:/Documents and Settings/sbtho/Desktop/downloads/samp.xml";
            string filename1 = "C:/Documents and Settings/sbtho/Desktop/downloads/sampdigsig.xml";
            xmlDoc.PreserveWhitespace = false;
            xmlDoc.Load(new XmlTextReader(filename));

            SignedXml signedXml = new SignedXml(xmlDoc);
            signedXml.SigningKey = rsaKey.Key;
            Signature xmlSignature = signedXml.Signature;

            Reference reference = new Reference("");
            XmlDsigEnvelopedSignatureTransform envelope = new XmlDsigEnvelopedSignatureTransform();
            XmlDsigC14NWithCommentsTransform envelope1 = new XmlDsigC14NWithCommentsTransform();
            reference.AddTransform(envelope);
            reference.AddTransform(envelope1);
            xmlSignature.SignedInfo.AddReference(reference);

            KeyInfo keyInfo = new KeyInfo();
             X509Store store = new X509Store(StoreName.TrustedPeople, StoreLocation.CurrentUser);
            store.Open(OpenFlags.ReadOnly);
            X509Certificate2Collection certs = store.Certificates.Find(X509FindType.FindByThumbprint, "ffa8ebf4760ab2d145b8ca21b1de258923e7d9d8", false);
            store.Close();
            keyInfo.AddClause(rsaKey);
            xmlSignature.KeyInfo = keyInfo;
            signedXml.ComputeSignature();

            XmlElement xmlDigSign = signedXml.GetXml();
            xmlDoc.DocumentElement.AppendChild(xmlDoc.ImportNode(xmlDigSign, true));

            if (xmlDoc.FirstChild.GetType() == typeof(XmlDeclaration))
                xmlDoc.RemoveChild(xmlDoc.FirstChild);

            XmlTextWriter xmlWriter = new XmlTextWriter(filename1, new UTF8Encoding(false));
            xmlDoc.WriteTo(xmlWriter);
            xmlWriter.Close();

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这就是我达到的程度。这是从trustedpeople商店读到的。现在如何将此证书插入到XML文档中？

这里，x509证书存储在x509certificate2collection对象类型中，要显示它应该存储在x509证书对象类型中

 X509Certificate2 cer=new X509Certificate2();
 if (certs.Count > 0)
            {
                cer = certs[0];
            };

现在可以使用keyinfo addclause将其添加到xml签名文档中

 keyInfo.AddClause(new KeyInfoX509Data(cer));