必应 API 查询对可观察集合的回调

使用这篇文章中的一些信息创建了一个Windows 应用商店应用程序：如何在 Windows Phone 中使用必应搜索 API？

目标

文本框 - 键入任何术语"搜索"按钮 - 搜索该术语并填充使用必应 API 检索的图片的 GridView

问题

我得到了图片，它们是通过我的"OnQueryComplete"回调接收的，但我无法弄清楚填充集合的正确方法是什么。由于我不知道如何等待这个电话，所以我（只是为了看看我是否可以让它工作，它确实如此）添加了一个 while 循环（您可能会看到问题）。正确的方法是什么？如何处理用于填充 GridView 并让它等到完成的回调？

当前视图模型代码

    public bool itemsFinished = false;
    private ObservableCollection<SearchResult> _ImageResults;
    public ObservableCollection<SearchResult> ImageResults {
        get {
            if (_ImageResults == null) {
                while (!itemsFinished) {
                    int i = 0;
                    i++;
                }
            }
            return _ImageResults;
        }
        set {
            _ImageResults = value;
        }
    }
    public SearchResultViewModel() {
       GetPictures("dogs");
    }

    public void GetPictures(string searchTerm) {
        // This is the query - or you could get it from args. 
        string query = searchTerm;
        // Create a Bing container. 
        string rootUri = "https://api.datamarket.azure.com/Bing/Search";
        var bingContainer = new Bing.BingSearchContainer(new Uri(rootUri));
        // Replace this value with your account key. 
        var accountKey = "myaccountkey";
        // Configure bingContainer to use your credentials. 
        bingContainer.Credentials = new NetworkCredential(accountKey, accountKey);
        // Build the query. 
        var imageQuery = bingContainer.Image(query, null, null, null, null, null, null);
        imageQuery.BeginExecute(OnQueryComplete, imageQuery);
        // var imageResults = imageQuery.Execute(); 
    }
    private void OnQueryComplete(IAsyncResult result) {
       // ImageResults.Clear();
        _ImageResults = new ObservableCollection<SearchResult>();
        var query = (DataServiceQuery<ImageResult>)result.AsyncState;
        var enumerableResults = query.EndExecute(result);
        int i = 0;
        foreach (var item in enumerableResults) {
            SearchResult myResult = new SearchResult();
            myResult.Title = item.Title;
            myResult.ImageUri = new Uri(item.MediaUrl);
            ImageResults.Add(myResult);
            i++;
            if (i >= 14) {
                break;
            }
        }
        itemsFinished = true;
    }

private ObservableCollection<SearchResult> _ImageResults;
public ObservableCollection<SearchResult> ImageResults {
    get
    {
        return _ImageResults;
    }
    set {
        _ImageResults = value;
    }
}
public SearchResultViewModel() {
   _ImageResults = new ObservableCollection<SearchResult>(); // Just create it once.
   GetPictures("dogs");
}
private void OnQueryComplete(IAsyncResult result) {
    _ImageResults.Clear(); // Clear isn't bad, that way you keep your reference to your original collection!
    //_ImageResults = new ObservableCollection<SearchResult>(); // We already have one. ObservableCollection works best if you keep on working with the collection you have.
    var query = (DataServiceQuery<ImageResult>)result.AsyncState;
    var enumerableResults = query.EndExecute(result);
    int i = 0;
    foreach (var item in enumerableResults) {
        SearchResult myResult = new SearchResult();
        myResult.Title = item.Title;
        myResult.ImageUri = new Uri(item.MediaUrl);
        ImageResults.Add(myResult);
        i++;
        if (i >= 14) {
            break;
        }
    }
}