通用Windows应用《博客园-开发者的网上家园》开发（1）——MVVM模式

 1 public class ViewModel : INotifyPropertyChanged
 2     {
 3         public ViewModel()
 4         {
 5             this.Blogs = new ObservableCollection<Blog>();
 6         }
 7 
 8         /// <summary>
 9         /// 加载某一页博客
10         /// </summary>
11         /// <param name="pageIndex">页码</param>
12         /// <param name="pageSize">多少条</param>
13         /// <returns></returns>
14         public async Task LoadBlogsAsync(int pageIndex, int pageSize)
15         {
16             string url = string.Format(BlogUrl, pageIndex, pageSize);
17             this.Blogs = XmlHelper.XmlToBlog(await new HttpClient().GetStringAsync(new Uri(url)));
18             IsBlogLoaded = true;
19         }
20 
21         /// <summary>
22         /// 加载下一页博客，并追加到当前数据源中
23         /// </summary>
24         /// <param name="count">加载多少条</param>
25         /// <returns></returns>
26         public async Task LoadMoreBlogsAsync(int count)
27         {
28             string url = string.Format(BlogUrl, ++App.CurrentBlogPage, count);
29             foreach (var item in XmlHelper.XmlToBlog(await new HttpClient().GetStringAsync(new Uri(url))))
30             {
31                 this.Blogs.Add(item);
32             }
33         }
34 
35         private ObservableCollection<Blog> _blogs;
36         public ObservableCollection<Blog> Blogs
37         {
38             get { return _blogs; }
39             private set
40             {
41                 if (value != _blogs)
42                 {
43                     _blogs = value;
44                     NotifyPropertyChanged("Blogs");
45                 }
46             }
47         }
48 
49         private const string BlogUrl = "http://wcf.open.cnblogs.com/blog/sitehome/paged/{0}/{1}";
50 
51         public bool IsLoaded { get; private set; }
52 
53         public event PropertyChangedEventHandler PropertyChanged;
54         private void NotifyPropertyChanged(string propertyName)
55         {
56             PropertyChangedEventHandler handler = PropertyChanged;
57             if (null != handler)
58             {
59                 handler(this, new PropertyChangedEventArgs(propertyName));
60             }
61         }
62     }