我目前正在开发一个应用程序，该应用程序加载一个加载了有关 WinPhanDev 社区中的开发人员信息的 XML，然后获取所有开发人员的推文。它还应该显示特定开发人员已发布的所有已发布应用程序，这是部分工作。
在运行解析从http://zunderstorehost.azurewebsites.net/api/获取的 json的代码时，在将第 5/6 或第 7 个开发人员添加到集合时，我会得到随机异常，而无需更改代码。
处理所有数据的整个方法包含以下代码：
async void webClient_DownloadStringCompleted(object sender, System.Net.DownloadStringCompletedEventArgs e)
{
if (e.Error == null)
{
string _proimage = "";
me.twitterClient = new RestClient("https://api.twitter.com");
me.tapiAuthToken = EncodeTo64(me.tapiCKey + ":" + me.tapiCSecret);
// Authorize app for Twitter
me.tweetReq = new RestRequest("oauth2/token", Method.POST);
me.tweetReq.AddHeader("Authorization", "Basic " + me.tapiAuthToken);
me.tweetReq.AddHeader("Host", "api.twitter.com");
me.tweetReq.AddHeader("User-Agent", "WinPhanDevs");
me.tweetReq.AddHeader("Content-Type", "application/x-www-form-urlencoded;charset=UTF8");
me.tweetReq.AddParameter("grant_type", "client_credentials");
try
{
me.resp = await me.twitterClient.GetResponseAsync(me.tweetReq);
me.token = Newtonsoft.Json.JsonConvert.DeserializeObject<OAuthToken>(me.resp.Content);
}
catch (Exception ex)
{
ErrorClass error = Newtonsoft.Json.JsonConvert.DeserializeObject<ErrorClass>(me.resp.Content);
App.ViewModel.Devs.Add(new WinPhanDevs.ViewModels.DevViewModel() { Name = error.errors[0].label, Twitter = error.errors[0].message, PublisherID = ex.Message, Site = "", StoryLink = "", Image= "", Tweets = null });
}
XMLData = XElement.Parse(e.Result);
var devs = from el in XMLData.Descendants("dev") select el;
foreach (XElement el in devs)
{
#region "Load devs tweets"
twts = new ObservableCollection<TweetViewModel>();
if(el.Attribute("twitter").Value != "")
{
// Fetch tweets
me.twitterClient = new RestClient(me.tapi);
me.tweetReq = new RestRequest("search/tweets.json", Method.GET);
me.tweetReq.AddHeader("Authorization", "Bearer " + me.token.access_token);
me.tweetReq.AddHeader("Accept-Encoding", "gzip");
me.tweetReq.AddParameter("q", "from:" + el.Attribute("twitter").Value + " exclude:retweets exclude:replies");
string[] _createdAt = new string[20];
string[] _text = new string[20];
string[] _link = new string[20];
string[] _image = new string[20];
Peep res = await ExecuteAsync<Peep>(me.tweetReq, me.tapi);
Status[] statuses = res.statuses;
int i = 0;
foreach (Status tweet in statuses)
{
DateTime time = DateTime.ParseExact(tweet.created_at, "ddd MMM dd HH:mm:ss zzz yyyy", new System.Globalization.CultureInfo("en-US"));
_createdAt[i] = time.ToShortDateString() + " " + time.ToShortTimeString();
_text[i] = tweet.text;
if (tweet.entities.urls.Length > 0) { _link[i] = tweet.entities.urls[0].expanded_url; _text[i] = _text[i].Replace(tweet.entities.urls[0].url, ""); } else { _link[i] = ""; }
if (tweet.entities.media != null) { _image[i] = tweet.entities.media[0].media_url; _text[i] = _text[i].Replace(tweet.entities.media[0].url, ""); } else { _image[i] = ""; }
twts.Add(new WinPhanDevs.ViewModels.TweetViewModel() { Date = _createdAt[i], Tweet = _text[i], Link = _link[i] });
i++;
}
_proimage = statuses[0].user.profile_image_url;
}
#endregion
#region "Load devs apps"
// Gets an IndexOutOfBounds/TargetInvocation/NullReference
// exception in here while adding the 5th/6th or 7th developer,
// none of the exceptions are caught.
// Without this whole region the app runs smooth.
try
{
RestClient devClient = new RestClient("http://zunderstorehost.azurewebsites.net/api/");
string dev = el.Attribute("pubid").Value;
//dev = dev.Replace(" ", "+");
RestRequest devReq = new RestRequest("WP8StoreAppList/Query/" + dev, Method.GET);
response = await devClient.GetContentAsync(devReq);
AppClass[] apps = JsonConvert.DeserializeObject<AppClass[]>(response);
Apps = new ObservableCollection<AppViewModel>();
foreach (AppClass app in apps)
{
string _price;
if (app.Offers.Count > 1)
{
if (app.Offers[0].Price != "0")
{
_price = app.Offers[0].DisplayPrice + " (Trial available)";
}
else
{
_price = app.Offers[1].DisplayPrice + " (Trial available)";
}
}
else
{
if (app.Offers[0].Price == "0")
{
_price = "FREE";
}
else
{
_price = app.Offers[0].DisplayPrice;
}
}
try
{
Apps.Add(new AppViewModel()
{
Name = app.Name,
ReleaseDate = app.ReleaseDate,
GUID = app.Guid,
Icon = app.Icon,
Price = _price,
Publisher = app.Publisher,
Version = app.Version,
StoreLink = ""
});
}catch (Exception ex)
{
Devs.Add(new DevViewModel() { Name = "Failed to add!", Apps = null, Image = "", PublisherID = "", Site="", StoryLink="", Tweets=null, Twitter=ex.Message});
}
}
}catch (Exception ex)
{
Devs.Add(new DevViewModel() { Name = "Failed to add!", Apps = null, Image = "", PublisherID = "", Site = "", StoryLink = "", Tweets = null, Twitter = ex.Message });
}
#endregion
try
{
Devs.Add(new DevViewModel() { Name = el.Attribute("name").Value, Twitter = el.Attribute("twitter").Value, Site = el.Attribute("web").Value, PublisherID = el.Attribute("pubid").Value, StoryLink = el.Attribute("story").Value, Tweets = twts, Image = _proimage, Apps = Apps });
}catch(Exception ex)
{
Devs.Add(new DevViewModel() { Name = "Failed to add!", Apps = null, Image = "", PublisherID = "", Site = "", StoryLink = "", Tweets = null, Twitter = ex.Message });
}
}
this.IsDataLoaded = true;
}
else
{
Devs.Add(new DevViewModel() { Name = e.Error.Source, Twitter = e.Error.Message, PublisherID = e.Error.InnerException.Message, Site = "", StoryLink = "" });
}
}
整个项目可在https://github.com/IzaacJ/WinPhanDevs获得，发生此问题的特定文件是 MainViewModel.cs
解决此问题的任何帮助将不胜感激！