Question

首先，我正在开发一个相当高级别的文件系统，我需要能够（非常精确定位）及时识别和处理文件。话虽如此，我正在使用一个将使用FileSystemWatcher的系统。然而，观察者的整个问题是当涉及大文件时抛出事件时往往会出现问题。

为了解决这个问题，我正在研究一个抽象类，它可以在文件系统观察者创建文件后单独处理这些文件。

我遇到的当前路障是我对文件的进程外验证正在抛出一个事件，我只是遇到了问题。

public abstract class absFile
    {
        public delegate void FileAvailable(object sender, FileEventArgs e);
        public event FileAvailable OnFileAvailable;

        public void isAvailable()
        {
            // Create a new threaded instance of the AvailableCheck private void
            // This method will be run out of process to allow other operations to continue.
            Thread toAvailableCheck = new Thread(new ThreadStart(AvailableCheck));

            // Once the threaded object is created, start it.
            toAvailableCheck.Start();
        }

 private void AvailableCheck()
        {
            // Declaring the file stream toThisFile to be used later with the File.Open
            FileStream toThisFile;

            // Declaring and instantiating the attempt counter for the loop
            int tiAttemptNumber = 0;

            // Declaring the event args for returning the events that are
            // used by this object.

            FileEventArgs toFileEventArgs = new FileEventArgs();

            do {
                try
                {
                    // Attempt to open the file.  If this fails the try
                    // will interrupt the processing and it will be caught.
                    toThisFile = File.Open(this.FilePath, FileMode.Open);

                    // If the file.open method does not fail, the isFileAvailable
                    // property will be set to true by updating the mbIsAvailable
                    // private boolean.
                    mbIsAvailable = true;

                    // populate the file event args to send back 
                    // the number of attempts made at the file and the pause lenght
                    toFileEventArgs.Attempts = tiAttemptNumber;
                    toFileEventArgs.Pause = this.AttemptPause / 1000;

                    // This event is called when the file is complete.
                    // The client application will be able to handle this event.
                    OnFileAvailable(this, toFileEventArgs);


                    // close and dispose of the filestream.
                    toThisFile.Close();
                    toThisFile.Dispose();
                }
                catch (Exception toException)
                {
                    // Since the open failed, add 1 to the counter so that
                    // it will eventually time out.
                    tiAttemptNumber++;

                    // Set the isFileAvailable property to false.  This property
                    // will default as false, but as a part of standard, make sure that
                    // if the open fails that the flag IS set to false by updating the 
                    // mbIsAvailable private boolean.
                    mbIsAvailable = false;

                    // Put the thread to sleep for the ammount of time specified
                    // by the AttemptPause.  This will give the file time to finish
                    // whatever process it is involved in.
                    Thread.Sleep(this.AttemptPause);
                }

              // Continue to make attempts until either the file is marked as available
              // or the number of current attempts is the same as or greater than the
              // AccessAttempts property.
            } while (!this.isFileAvailable && this.AccessAttempts > tiAttemptNumber);
        }

这是我正在运行的代码，你可以在private void AvailableCheck中看到，OnfileAvailable是一个名为passen this的委托和文件事件args。

现在我继承了这个抽象类，我需要能够捕获那个事件。

        toWatcher.Created += new FileSystemEventHandler(OnCreated);

在主要调用

，在代码中向下调用以下方法

private void OnCreated(object source, FileSystemEventArgs e)
{
    lstStatus.Invoke(new MethodInvoker(delegate { 
        lstStatus.Items.Add(DateTime.Now.ToString("g") + " - " + e.Name + " - File Created Event Detected for: " + e.FullPath);
        lstStatus.TopIndex = lstStatus.Items.Count - 1;
        tgtFile ThisFile = new tgtFile(e.FullPath);
        lstStatus.Items.Add(DateTime.Now.ToString("g") + " - " + e.Name + " - Creating tgtFile Object");
    }));
}

tgtFile对象的instatiation传递路径，该路径沿着长矛向下移动到可用方法。

正如您所看到的，存在从tgtFile对象触发OnFileAvailable事件的可能性。

同样如你所见，基于filesystemwatcher的线程设计，同时存在多个tgtFile对象存在于内存中的可能性。

在我的主应用程序中，然后我希望能够做类似的事情：

public tgtFile ThisFile;
ThisFile.OnFileAvailable += new EventHandler(OnFileAvailable);

但是EventHandler出错了，这就是我被困住的地方。

Answer 1

如果它给你一个编译器错误，可能是因为你在这行中引用的“OnFileAvailable”方法（来自帖子的底部）：

ThisFile.OnFileAvailable += new EventHandler(OnFileAvailable);

不期待EventHandler - 它期待FileAvailable代表。将其更改为：

ThisFile.OnFileAvailable += new absFile.FileAvailable(OnFileAvailable);
//note that this can also just be ThisFile.OnFileAvailable += OnFileAvailable;

并确保OnFileAvailable如下所示：

public void OnFileAvailable(object sender, FileEventArgs e)
{
   //...
}

Answer 2

首先要做的事情......在调用之前确保事件已订阅。将事件调用包装在IF语句中：

if (OnFileAvailable != null)
    OnFileAvailable(this, toFileEventArgs);

需要一点帮助才能捕获在单独线程中引发的事件

2 个答案: