无法将 JSON 字符串反序列化为包含包含对象数组的对象的对象

我有一个从 Web 服务调用返回的 JSON 对象，如下所示：

{"responseData":{"results":[{
    "mothraId":null,
    "studentId":null,
    "bannerPIdM":null,
    "externalId":null,
    "dFirstName":null,
    "dFullName":null,
    "dLastName":null,
    "dMiddleName":null,
    "modifyDate":"2012-02-24 06:24:33",
    "oFirstName":"Joe",
    "oFullName":"Joe R Smith",
    "oLastName":"Smith",
    "oMiddleName":"R",
    "iamId":"999999999",
    "ppsId":"999999999",
    "oSuffix":null,
    "dSuffix":null,
    "isEmployee":null,
    "isHSEmployee":null,
    "isFaculty":"N",
    "isStudent":"N",
    "isStaff":"N",
    "isExternal":"N",
    "privacyCode":null}]},
"responseStatus":0,
"responseDetails":""}

我正在尝试使用以下方法将 JSON 字符串反序列化为对象：

ReturnObject allInOne = js.Deserialize<ReturnObject>(jsonResponse);

返回对象定义如下：

public class ReturnObject
{
    public String responseDetails { get; set; }
    public String responseCode { get; set; }
    public ResponseData responseData { get; set; }
    public class ResponseData
    {
        public List<PeopleResult> results { get; set; }
        public class PeopleResult{
            String iamId { get; set; }
            String mothraId { get; set; }
            String ppsId { get; set; }
            String studentId { get; set; }
            String bannerPIdM { get; set; }
            String externalId { get; set; }
            String oFirstName { get; set; }
            String oMiddleName { get; set; }
            String oLastName { get; set; }
            String oFullName { get; set; }
            String oSuffix { get; set; }
            String dFirstName { get; set; }
            String dMiddleName { get; set; }
            String dLastName { get; set; }
            String dSuffix { get; set; }
            String dFullName { get; set; }
            String isEmployee { get; set; }
            String isHSEmployee { get; set; }
            String isFaculty { get; set; }
            String isStudent { get; set; }
            String isStaff { get; set; }
            String isExternal { get; set; }
            String privacyCode { get; set; }
            String modifyDate { get; set; }
        }
    }

不幸的是，我得到了除列表结果中各个 PeopleResult 对象的内容之外的所有内容。 PeopleResult 中所有属性的值均为 null。 我的 ReturnObject 类的结构或命名是否有问题？