c# - File.Delete 问题与 filestream.write()

Question

我有刷新按钮。刷新时，我需要下载一个文件并反序列化其内容以读取其中的信息。以下是用于下载文件的方法。

public void DownloadVersionContents(long fileID,string fileName)
        {
            if (File.Exists(path))
              {
                 File.Delete(path);
              }
            Stream stream = service.DownloadContent(fileID);

            using (FileStream fileStream = File.OpenWrite(fileName))
            {
                // Write the stream to the file on disk.
                var buf = new byte[1024];
                int numBytes;
                while ((numBytes = stream.Read(buf, 0, buf.Length)) > 0)
                {
                    fileStream.Write(buf, 0, numBytes);
                }
                fileStream.Close();
            }
            stream.Close();
        }

每次单击刷新按钮时，我都必须删除文件并从服务器下载最新文件。如果在一两秒内调用刷新，我会收到一条错误消息

System.IO.IOException was caught
  HResult=-2147024864
  Message=The process cannot access the file 'C:\Users\...\AppData\Local\Temp\mapping - copy.xml' because it is being used by another process.
  Source=mscorlib
  StackTrace:
       at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
       at System.IO.File.InternalDelete(String path, Boolean checkHost)
       at System.IO.File.Delete(String path)

如果在至少 10 或 20 秒后调用刷新，我不会收到任何错误。该文件从未打开或使用过。请帮忙。编辑:抱歉，我忘了说，我在调用刷新后立即使用此方法反序列化文件。

public static T DeSerializeFromFile<T>(string xmlFilePath) 
        {
            T instance = default(T);

            if (xmlFilePath != null)
            {
                var reader = new StreamReader(xmlFilePath);
                var serializer = new XmlSerializer(typeof(T));
                instance = (T)serializer.Deserialize(reader);
            }
            return instance;
        }

更新值后再次调用刷新按钮。

Answer 1

这似乎是使用 try catch block 的好时机。捕获异常并在文件繁忙时提示用户。

try
{
    if (File.Exists(path))
         File.Delete(path);

    using(Stream stream = service.DownloadContent(fileID))
    {
        using (FileStream fileStream = File.OpenWrite(fileName))
        {
            // Write the stream to the file on disk.
            var buf = new byte[1024];
            int numBytes;
            while ((numBytes = stream.Read(buf, 0, buf.Length)) > 0)
            {
                fileStream.Write(buf, 0, numBytes);
            }
        }
    }
}
catch (IOException e)
{
    MessageBox.Show("The refresh failed, try again in a few seconds."); 
}

这不会加快刷新过程，但会防止用户通过垃圾刷新使您的程序崩溃。尝试在使用外部资源时始终存在这种异常处理。