下面是一些解決方案，可能有些用戶矯枉過正。我創建了一個新的靜態類，它有一個只在文件完成複製時觸發的事件。
用戶通過調用FileAccessWatcher.RegisterWaitForFileAccess(filePath)來註冊他們想要觀看的文件。如果該文件尚未被監視，則開始一個新的任務，該任務重複檢查該文件以查看是否可以打開該文件。每次它檢查它也讀取文件大小。如果文件大小在預定義的時間內沒有增加（在我的例子中是5分鐘），則退出循環。
當循環從可訪問的文件退出或從超時中觸發事件時。
public class FileAccessWatcher
{
// this list keeps track of files being watched
private static ConcurrentDictionary<string, FileAccessWatcher> watchedFiles = new ConcurrentDictionary<string, FileAccessWatcher>();
public static void RegisterWaitForFileAccess(string filePath)
{
// if the file is already being watched, don't do anything
if (watchedFiles.ContainsKey(filePath))
{
return;
}
// otherwise, start watching it
FileAccessWatcher accessWatcher = new FileAccessWatcher(filePath);
watchedFiles[filePath] = accessWatcher;
accessWatcher.StartWatching();
}
/// <summary>
/// Event triggered when the file is finished copying or when the file size has not increased in the last 5 minutes.
/// </summary>
public static event FileSystemEventHandler FileFinishedCopying;
private static readonly TimeSpan MaximumIdleTime = TimeSpan.FromMinutes(5);
private readonly FileInfo file;
private long lastFileSize = 0;
private DateTime timeOfLastFileSizeIncrease = DateTime.Now;
private FileAccessWatcher(string filePath)
{
this.file = new FileInfo(filePath);
}
private Task StartWatching()
{
return Task.Factory.StartNew(this.RunLoop);
}
private void RunLoop()
{
while (this.IsFileLocked())
{
long currentFileSize = this.GetFileSize();
if (currentFileSize > this.lastFileSize)
{
this.lastFileSize = currentFileSize;
this.timeOfLastFileSizeIncrease = DateTime.Now;
}
// if the file size has not increased for a pre-defined time limit, cancel
if (DateTime.Now - this.timeOfLastFileSizeIncrease > MaximumIdleTime)
{
break;
}
}
this.RemoveFromWatchedFiles();
this.RaiseFileFinishedCopyingEvent();
}
private void RemoveFromWatchedFiles()
{
FileAccessWatcher accessWatcher;
watchedFiles.TryRemove(this.file.FullName, out accessWatcher);
}
private void RaiseFileFinishedCopyingEvent()
{
FileFinishedCopying?.Invoke(this,
new FileSystemEventArgs(WatcherChangeTypes.Changed, this.file.FullName, this.file.Name));
}
private long GetFileSize()
{
return this.file.Length;
}
private bool IsFileLocked()
{
try
{
using (this.file.Open(FileMode.Open)) { }
}
catch (IOException e)
{
var errorCode = Marshal.GetHRForException(e) & ((1 << 16) - 1);
return errorCode == 32 || errorCode == 33;
}
return false;
}
}
用法示例：
// register the event
FileAccessWatcher.FileFinishedCopying += FileAccessWatcher_FileFinishedCopying;
// start monitoring the file (put this inside the OnChanged event handler of the FileSystemWatcher
FileAccessWatcher.RegisterWaitForFileAccess(fileSystemEventArgs.FullPath);
處理好FileFinishedCopyingEvent：
private void FileAccessWatcher_FileFinishedCopying(object sender, FileSystemEventArgs e)
{
Console.WriteLine("File finished copying: " + e.FullPath);
}
可能重複[有沒有辦法檢查一個文件是否正在使用？]（http://stackoverflow.com/questions/876473/is-there-a-way-to-check-if-a-file-is-in -use） – 2015-09-25 07:28:18
這段代碼有一個'File.Create（fileName）'的簡單錯誤。答案缺少這一點。沒有必要等待關閉。 – usr 2016-03-31 11:14:10