public async Task <string> RequestCheckExistAppointmentAsync(AppointmentJson json) { //Create Dialog //Create Parameter to POST request Dictionary <string, object> data = new Dictionary <string, object>(); data.Add("username", json.UserName); data.Add("appointmentdate", json.AppointmentDate); data.Add("appointmenttime", json.AppointmentTime); string response = await myAPI.ExistAppointment(data); return(response); }