删除图片框中显示的文件

Question

我正在从openfiledialoge中选择文件并将其显示在图片框中,当我点击delete按钮时,它在文本框中显示我正在异常The process cannot access the file because it is being used by another process. 我搜索了很多这个例外以便得到解决,但是当我尝试关闭时,我没有解决任何问题带有imagename的文件,它位于文本框中,即我在图片框中显示的文件; 使用IsFileLocked方法,这会关闭并删除特定目录路径的所有文件,但是如何删除picturebox中显示的唯一文件,我哪里出错了

     public partial class RemoveAds : Form
    {
        OpenFileDialog ofd = null;
        string path = @"C:\Users\Monika\Documents\Visual Studio 2010\Projects\OnlineExam\OnlineExam\Image\"; // this is the path that you are checking.

        public RemoveAds()
        {
            InitializeComponent();
        }


        private void button1_Click(object sender, EventArgs e)
        {
            if (System.IO.Directory.Exists(path))
            {
                 ofd = new OpenFileDialog();
                ofd.InitialDirectory = path;
                DialogResult dr = new DialogResult();
                if (ofd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
                {
                    Image img = new Bitmap(ofd.FileName);
                    string imgName = ofd.SafeFileName;
                    txtImageName.Text = imgName;
                    pictureBox1.Image = img.GetThumbnailImage(350, 350, null, new IntPtr());
                    ofd.RestoreDirectory = true;
                }
            }
            else
            {
                return;
            } 
        }
private void button2_Click(object sender, EventArgs e)
        {
            //Image img = new Bitmap(ofd.FileName);
            string imgName = ofd.SafeFileName;  
             if (Directory.Exists(path))
             {

                 var directory = new DirectoryInfo(path);
                 foreach (FileInfo file in directory.GetFiles())
                 { if(!IsFileLocked(file))
                     file.Delete(); 
                 }
             }


        }
        public static Boolean IsFileLocked(FileInfo path)
        {
            FileStream stream = null;   
            try
            { //Don't change FileAccess to ReadWrite,
                //because if a file is in readOnly, it fails.
                stream = path.Open ( FileMode.Open, FileAccess.Read, FileShare.None ); 
            } 
            catch (IOException) 
            { //the file is unavailable because it is:
                //still being written to or being processed by another thread
                //or does not exist (has already been processed)
                return true;
            } 
            finally
            { 
                if (stream != null)
                    stream.Close();
            }   
            //file is not locked
            return false;
        }
    }

在此先感谢您的帮助

Answer 1

(先前)接受的这个问题的答案是非常糟糕的做法.如果你阅读文档上System.Drawing.Bitmap,特别是创建从文件中位图超载,你会发现:

文件保持锁定状态,直到处理掉位图.

在您的代码中,您创建位图并将其存储在本地变量中,但是在完成后您永远不会将其丢弃.这意味着您的图像对象已超出范围,但尚未对您尝试删除的图像文件释放锁定.对于所有实现的对象IDisposable(如Bitmap),您必须自己处理它们.例如,请查看此问题(或搜索其他人 - 这是一个非常重要的概念!).

要正确纠正问题,您只需在完成后处理图像:

 if (ofd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
 {
      Image img = new Bitmap(ofd.FileName);  // create the bitmap
      string imgName = ofd.SafeFileName;
      txtImageName.Text = imgName;
      pictureBox1.Image = img.GetThumbnailImage(350, 350, null, new IntPtr());
      ofd.RestoreDirectory = true;
      img.Dispose();  // dispose the bitmap object
 }

请不要接受以下答案中的建议 - 您几乎不需要打电话GC.Collect,如果您需要这样做以使工作正常,那么这应该是一个非常强烈的信号,表明您正在做其他错误的事情.

此外,如果您只想删除一个文件(您显示的位图),则删除代码错误,并且还会删除目录中的每个文件(这只是重复Adel的观点).此外,OpenFileDialog我不建议只保存一个全局对象来存储文件名,而是建议摆脱它并保存文件信息:

FileInfo imageFileinfo;           //add this
//OpenFileDialog ofd = null;      Get rid of this

private void button1_Click(object sender, EventArgs e)
{
     if (System.IO.Directory.Exists(path))
     {
         OpenFileDialog ofd = new OpenFileDialog();  //make ofd local
         ofd.InitialDirectory = path;
         DialogResult dr = new DialogResult();
         if (ofd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
         {
              Image img = new Bitmap(ofd.FileName);
              imageFileinfo = new FileInfo(ofd.FileName);  // save the file name
              string imgName = ofd.SafeFileName;
              txtImageName.Text = imgName;
              pictureBox1.Image = img.GetThumbnailImage(350, 350, null, new IntPtr());
              ofd.RestoreDirectory = true;
              img.Dispose();
         }
         ofd.Dispose();  //don't forget to dispose it!
     }
     else
     {
         return;
     }
 }

然后在第二个按钮处理程序中,您可以删除您感兴趣的文件.

        private void button2_Click(object sender, EventArgs e)
        {                
           if (!IsFileLocked(imageFileinfo))
            {                 
                imageFileinfo.Delete();
            }
        }