为什么我的列表在函数调用中被分配后为空

这可能是一个愚蠢的问题。但是当我修改Live SDK示例中的一个示例时，出现了一个奇怪的问题。

我认为根本原因是异步函数GetAll()是同步使用的。

下面是代码片段，我把问题作为注释。提前感谢!

class SkyeDriveViewModel: INotifyPropertyChanged
{
    private List<SkyDriveItem> folderList = null;
    public List<SkyDriveItem> FolderList
    {
        get { return folderList; }
        private set
        {
            if (value != folderList)
            {
                folderList = value;
                NotifyPropertyChanged("FolderList");
            }
        }
    }
    private async void GetAll(string desiredPath)
    {
        FolderList = new List<SkyDriveItem>();
        this.liveClient = new LiveConnectClient(SkyDrivePage.Session);
        try
        {
            LiveOperationResult operationResult = await this.liveClient.GetAsync(desiredPath);
            dynamic result = operationResult.Result;
            dynamic items = result.data;
            foreach (dynamic item in items)
            {
                SkyDriveItem newItem = new SkyDriveItem(item);
                if (newItem.IsFolder)
                {
                    FolderList.Add(newItem);
                }
            }
        }
        catch (LiveConnectException e)
        {
        }
        //**till here, FolderList was assigned**
    }
    public void InitList()
    {
        Debugger.Log();
        GetAll(SKYDRIVEINITPATH);
        Debugger.LogWhen(eDebugger.LogTiming.Exit); 
        //**till here, FolderList had zero item**
    }
}