public void UpdatePosts()
{
if (this._updateTask != null)
{
this._updateTask.Cancel();
}
// load posts from the network
string postsUrl = this._urlBuilder.BuildPostsUrl(this.BoardName, this.ThreadNumber);
this._updateTask = new HttpGetJsonTask<PostListModel>(postsUrl, this.OnPostsLoadedAfterUpdate);
this._updateTask.OnError = this.ShowErrorAfterUpdate;
this._updateTask.OnProgressChanged = val => this.ProgressAfterUpdate = val;
this.IsLoadingAfterUpdate = true;
this._updateTask.Execute();
}