limesurvey api add_participants method cannot add participant

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Your LimeSurvey version: LimeSurvey Community Edition
Version 5.3.26+220720
Own server or LimeSurvey hosting: Own server
Survey theme/template: fruity
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(Write here your question/remark)
I call limesurvey api add_participants  method  with c#.
Respose message is equal to request 
there is no error. But i can't see adding participant in my survey in portal.
Can you explain how can i call add_participant method step by step via JSONRPC
My c# code : 
                client.Method = "add_participants";
                client.Parameters.Add("sSessionKey", SessionKey);

                client.Parameters.Add("iSurveyID", sid);

       
                var Listeklejson = JsonConvert.SerializeObject(surveyParticipantList);


                client.Parameters.Add("aParticipantData", Base64Encode(Listeklejson));

                client.Parameters.Add("bCreateToken", false);
;
                client.Post();

 

List<aParticipantData> Listekle = new List<aParticipantData>();
aParticipantData ekle = new aParticipantData { email = "This email address is being protected from spambots. You need JavaScript enabled to view it.", lastname = "test", firstname = "test", language = "tr" , emailstatus = "OK" };
Listekle.Add(ekle);

Hi. One thing that tripped me up is that you have to send an array of participants to add_participants and not a single participant. If you are only adding one participant, you still need to send it as a single element of an array. I'm a php coder so my apologies about the syntax difference, but you have to pass this:

and NOT this:

That may not be your issue, but thought I'd throw in what tripped me up just in case.