如何验证加密的mime实体，并使用“”application/pkcs7-mime签名格式

当我解密签名和加密的消息时，我成功解密并得到一个"MimeEntity"，他的smime类型是"signed-data"

，但签名格式不是"multipart/signed"，格式是"application/pkcs7-mime"。

我将其转换为"ApplicationPkcs7Mime"，"multipart"，"textpart"，"messagepart"，但我得到"null"值。

但是我可以在outlook中正常打开此消息，我使用outlook发送此消息，内容不是"mimikit"生成的。

我将只转换"消息"。体"到"ApplicationPkcs7Mime"，但关于"解密mime实体"我该怎么办?

代码:

var parser = new MimeParser(new MemoryStream(content), MimeFormat.Default);
   MimeMessage  message = parser.ParseMessage();

        if (message.Body is  ApplicationPkcs7Mime) {
            using (var ctx = new MySecureMimeContext()) {  
                var encrypted = message.Body as ApplicationPkcs7Mime;
                if (encrypted != null && encrypted.SecureMimeType == SecureMimeType.EnvelopedData){
                    ctx.Import(new MemoryStream(p12data.blob),p12data.Pwd);
                    MimeEntity decrypted = encrypted.Decrypt(ctx);
                    if (decrypted is MultipartSigned) {                          
                        var signed = (MultipartSigned)decrypted;
                        var protocol = signed.ContentType.Parameters["protocol"];
                        if (ctx.Supports(protocol)){
                            if (signed[0] is TextPart && signed[1] is ApplicationPkcs7Signature) {
                                var extracted = (TextPart)signed[0];
                                var signatures = signed.Verify(ctx);
                                if (signatures != null && signatures.Count > 0) {
                                    foreach (var signature in signatures){
                                        bool valid = signature.Verify();
                                        if (!valid){
                                            isverify = false;
                                            return isverify;
                                        }
                                    }
                                }
                            }
                        }
                    }
                    else {
                        string signType = decrypted.ContentType.Parameters["smime-type"];                
                        if (signType == "signed-data"){    
                            //what can 1 do?
                            var signed = message.Body as ApplicationPkcs7Mime;
                        }                           
                    }
                }

else {
    string signType = decrypted.ContentType.Parameters["smime-type"];                
    if (signType == "signed-data"){    
        //what can 1 do?
        var signed = message.Body as ApplicationPkcs7Mime;
    }                           
}

else if (decrypted is ApplicationPkcs7Mime) {
    var signed = (ApplicationPkcs7Mime) decrypted;
    if (signed.SecureMimeType == SecureMimeType.SignedData) {
        // extract the original content and get a list of signatures
        MimeEntity original;
        // Note: if you are rendering the message, you'll want to render the
        // original mime part rather than the application/pkcs7-mime part.
        foreach (var signature in pkcs7.Verify (out original)) {
            try {
                bool valid = signature.Verify ();
                // If valid is true, then it signifies that the signed content
                // has not been modified since this particular signer signed the
                // content.
                // 
                // However, if it is false, then it indicates that the signed
                // content has been modified.
            } catch (DigitalSignatureVerifyException) {
                // There was an error verifying the signature.
            }
        }
    }
}