c# - 使用 FileSystemWatcher 触发事件，然后删除新创建的文件？

Question

我有一个使用 FileSystemWatcher 的 Windows 服务来监视文件夹、打印添加的图像，然后在打印后删除图像。

 private void bw_DoWork(object sender, DoWorkEventArgs e)
        {
            FileSystemWatcher Watcher = new FileSystemWatcher();
            Watcher.Path = @"C:\Images";
            Watcher.Created += new FileSystemEventHandler(Watcher_Changed);
            Watcher.EnableRaisingEvents = true;
        }

        private void Watcher_Changed(object sender, FileSystemEventArgs e)
        {
            try
            {
                PrintDocument myDoc = new PrintDocument();
                myDoc.PrintPage += new PrintPageEventHandler(print);
                FilePath = e.FullPath;
                myDoc.PrinterSettings.PrinterName = @"\\Network Printer";
                myDoc.Print();
                using (StreamWriter sw = new StreamWriter("C:\\error.txt"))
                {
                    sw.WriteLine("Printed File: " + FilePath);
                }
                File.Delete(e.FullPath);
            }
            catch(Exception excep)
            {
                using (StreamWriter sw = new StreamWriter("C:\\error.txt"))
                {
                    sw.WriteLine("Error: " + excep.ToString());
                }
            }
        }

问题是我抛出异常 Error: System.IO.IOException: The process cannot access the file because it is being used by another process. that the file is being used by another当我尝试删除它时的过程。我猜这是因为 FileSystemWatcher 保留了对它的某种引用。知道在这里做什么，打印后删除文件吗？

编辑: 之前没有在我的代码中包含此功能:

private void print(object sender, PrintPageEventArgs e)
        {
            try
            {
                using (Image i = Image.FromFile(FilePath))
                {
                    Point p = new Point(0, 0);
                    e.Graphics.DrawImage(i, p);
                }
            }
            catch(Exception exep)
            {
                throw exep;
            }
        }

我也对这个函数应用了 using block 建议，但也将删除移动到这个函数，它是 mydoc.EndPrint 的事件处理程序，以确保切断与文件的所有联系，这似乎可以解决问题。

void myDoc_EndPrint(object sender, PrintEventArgs e)
{
    File.Delete(FilePath);
}

Answer 1

PrintDocument 实现了 IDisposable，您需要确保它通过将其包装在 using block 中来释放它的文件句柄。

private void bw_DoWork(object sender, DoWorkEventArgs e)
    {
        FileSystemWatcher Watcher = new FileSystemWatcher();
        Watcher.Path = @"C:\Images";
        Watcher.Created += new FileSystemEventHandler(Watcher_Changed);
        Watcher.EnableRaisingEvents = true;
    }
private void Watcher_Changed(object sender, FileSystemEventArgs e)
{
    try
    {
        using (PrintDocument myDoc = new PrintDocument())
        {
            myDoc.PrintPage += new PrintPageEventHandler(print);
            FilePath = e.FullPath;
            myDoc.PrinterSettings.PrinterName = @"\\Network Printer";
            myDoc.Print();
            using (StreamWriter sw = new StreamWriter("C:\\error.txt"))
            {
                 sw.WriteLine("Printed File: " + FilePath);
            }
        }
        File.Delete(e.FullPath);
    }
    catch(Exception excep)
    {
        using (StreamWriter sw = new StreamWriter("C:\\error.txt"))
        {
            sw.WriteLine("Error: " + excep.ToString());
        }
    }
}