Facebook在应用程序内执行（无需在Safari或本机应用程序中打开）(Facebook Implementation within app (without opening in safari or native app))

 要获取AppData目录，最好使用GetFolderPath方法： 
 
Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData)
 
 %AppData%是一个环境变量，并且它们不会在.NET中的任何位置自动扩展，但您可以明确地使用Environment.ExpandEnvironmentVariable方法。 我仍然强烈建议您使用GetFolderPath ，因为约翰内斯·罗塞尔在评论中指出，在某些情况下，可能不会设置%AppData% 。 
 
 最后，创建路径，如您的示例所示： 
 
var fileName = Path.Combine(Environment.GetFolderPath(
    Environment.SpecialFolder.ApplicationData), "DateLinks.xml");

To get the AppData directory, it's best to use the GetFolderPath method:
 
Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData)
 
(must add using System if not present).
 
%AppData% is an environment variable, and they are not automatically expanded anywhere in .NET, although you can explicitly use the Environment.ExpandEnvironmentVariable method to do so. I would still strongly suggest that you use GetFolderPath however, because as Johannes Rössel points out in the comment, %AppData% may not be set in certain circumstances.
 
Finally, to create the path as shown in your example:
 
var fileName = Path.Combine(Environment.GetFolderPath(
    Environment.SpecialFolder.ApplicationData), "DateLinks.xml");