C# datacontract json序列化程序中的强制转换异常无效

我正在Visual Studio 2010中为Windows Phone 7.1开发一个项目。我正在尝试下载JSON数据并将其反序列化到对象列表中。下面是我用来构建web请求和处理响应的代码

public class HttpGetTask<T>
{
    public HttpGetTask(string url, Action<T> onPostExecute)
    {
        this.Url = url;
        this.OnPostExecute = onPostExecute;
    }

    public void Execute()
    {
        MessageBox.Show("We are in the task Execute method");
        if (this.OnPreExecute != null)
        {
            this.OnPreExecute();
        }

        // create the http request
        HttpWebRequest httpWebRequest = WebRequest.CreateHttp(this.Url);
        httpWebRequest.Method = "GET";
        httpWebRequest.Accept = "application/json";

        // get the response asynchronously
        httpWebRequest.BeginGetResponse(OnGetResponseCompleted, httpWebRequest);
    }

    private void OnGetResponseCompleted(IAsyncResult ar)
    {
        MessageBox.Show("We are in the OnGetResponseCompleted Method");
        var httpWebRequest = (HttpWebRequest)ar.AsyncState;

        // get the response
        HttpWebResponse response;
        try
        {
            response = (HttpWebResponse)httpWebRequest.EndGetResponse(ar);
        }
        catch (WebException e)
        {
            this.InvokeOnErrorHandler("Unable to connect to the web page.");
            return;
        }
        catch (Exception e)
        {
            this.InvokeOnErrorHandler(e.Message);
            return;
        }

        if (response.StatusCode != HttpStatusCode.OK)
        {
            this.InvokeOnErrorHandler((int)response.StatusCode + " " + response.StatusDescription);
            return;
        }

        // response stream
        var stream = response.GetResponseStream();

        // deserialize json
        var jsonSerializer = new DataContractJsonSerializer(typeof(T));
        var responseObject = (T)jsonSerializer.ReadObject(stream);

        // call the virtual method
        this.InvokeInUiThread(() => this.OnPostExecute(responseObject));
    }

---

当我运行我的应用程序时，在创建序列化程序对象时，或者在jsonserializer.ReadObject（流）行上，我得到一个无效的强制转换异常。关于发生这种情况的原因，您有什么想法吗？

请尝试使用int指定属性：

[DataMember(Name = "oid")]
public string Oid { get; set; }

应该是

[DataMember(Name = "oid")]
public int Oid { get; set; }

---

尝试使用int指定属性：

[DataMember(Name = "oid")]
public string Oid { get; set; }

应该是

[DataMember(Name = "oid")]
public int Oid { get; set; }