您需要在标题中指定content-type：
request.AddHeader("Content-type", "application/json");还
AddParameter根据方法添加到POST或URL查询字符串
我认为您需要像这样将其添加到主体中：
request.AddJsonBody( new { UserName = "UAT1206252627", SecurityQuestion = securityQuestion }); // AddJsonBody serializes the object automatically
