c# - 移动文件 3 次时出现异常

Question

当我将同一个文件复制 3 次到文件夹 A 时，为什么会出现 IOException(进程无法访问该文件，因为它正在被另一个进程使用。)

class FileWatcher {

    FileSystemWatcher fsw;
    FileInfo file;
    string destination = @"C:\FileMover\B\";
    Random random;

    public FileWatcher() {
        fsw = new FileSystemWatcher();
        random = new Random();           

        fsw.Path = @"C:\FileMover\A";

        fsw.Created += fsw_Created;

        fsw.EnableRaisingEvents = true;
    }

    void fsw_Created(object sender, FileSystemEventArgs e) {            
        string destinationFileName = destination + e.Name;

        if (!File.Exists(destinationFileName)) {
            file = new FileInfo(e.FullPath);
            file.MoveTo(destinationFileName);
        }
        else {
            file = new FileInfo(e.FullPath);                
            file.MoveTo(destinationFileName + random.Next());
        }
        file = null;                       
    }  
}

主要内容:

class Program {      
    static void Main(string[] args) {

        FileWatcher watcher = new FileWatcher();

        while (Console.ReadKey().Key != ConsoleKey.Q) {

        }
    }
}

2 次后文件夹 B 包含 2 个文件(sourceFileName 和 sourceFileName1274968236)

当我调试该部分时，不会抛出任何异常。

Answer 1

Created 可能会在文件刷新(？)到目标位置之前引发。尝试使用 Changed 并检查 e.ChangeType==WatcherChangeTypes.Created。

引用:http://msdn.microsoft.com/en-us/library/system.io.filesystemwatcher.created(v=vs.110).aspx

编辑:Changed 事件在 Created 之后引发，如果这是由于竞争条件引起的，可能会有所帮助，但问题仍可能发生。

The OnCreated event is raised as soon as a file is created. If a file is being copied or transferred into a watched directory, the OnCreated event will be raised immediately, followed by one or more OnChanged events.

找到这个:Wait Until File Is Completely Written还有这个:Is there a way to check if a file is in use?