C#: How to check if a open file has been updated

Question

You know the feature for example, you opened C:\\test.txt if you also have the same file in another editor, and you edit it there, when you return, the app will prompt that the file has changed, whether you want to update it. How do I check if the file has been updated?

UPDATE

Asked a sister question " Using FileSystemWatcher to watch for changes to files "

Answer 1

您可以使用FileSystemWatcher从文件系统获取通知。

Answer 2

使用FileSystemWatcher （首选）或定期比较上次修改日期。

Answer 3

You can either use a FileSystemWatcher , or you can poll for changes at opportune moments.

Note that the FileSystemWatcher may miss changes if under heavy load and is IDisposable . Failure to dispose it properly can cause stability issues (which I've had happen, personally). If you opt for polling, note that FileInfo caches some metadata so you'll need to call the FileInfo.Refresh method if you reuse FileInfo objects. Alternatively, use the File API.

For only a few files, polling is easier and safer to get right since it avoids the OS callback issues of FileSystemWatcher and never misses any events. For large number of files, the FileSystemWatcher is a must to achieve reasonable performance.