Question

我有用于备份主机文件的代码。当我运行代码时，我收到以下错误：

mscorlib.dll中出现未处理的“System.UnauthorizedAccessException”类型异常

奇怪的是文件正在被复制。我不确定代码是指什么，因为如果异常本身没有被抛出，一切都会按顺序排列（或者看起来如此）。

代码如下：

private void BackUpHost()
        {
            string fileName = "hosts";
            string newFileName = "hosts.bak";
            string sourcePath = @"c:\windows\system32\drivers\etc";
            string targetPath = @"c:\windows\system32\drivers\etc";

            string sourceFile = System.IO.Path.Combine(sourcePath, fileName);
            string destFile = System.IO.Path.Combine(targetPath, newFileName);

            if (!System.IO.Directory.Exists(targetPath))
            {
                System.IO.Directory.CreateDirectory(targetPath);
            }

            System.IO.File.Copy(sourceFile, destFile, true);

            if (System.IO.Directory.Exists(sourcePath))
            {
                    fileName = System.IO.Path.GetFileName(sourcePath);
                    destFile = System.IO.Path.Combine(targetPath, newFileName);
                    System.IO.File.Copy(sourcePath, destFile, true);

            }
            else
            {
                Console.WriteLine("Source path does not exist!");
            }
        }

Answer 1

为了解释我在评论中的意思，让我们“逐步”完成您的代码，并说明您获得异常的原因。下面的过程与将断点放入代码并使用 F10 跳过每个断点并查看调试器窗口的“局部变量”部分的过程相同。

private void BackUpHost()
{
  string fileName = "hosts";
  string newFileName = "hosts.bak";
  string sourcePath = @"c:\windows\system32\drivers\etc";
  string targetPath = @"c:\windows\system32\drivers\etc";

  string sourceFile = System.IO.Path.Combine(sourcePath, fileName);
  // sourceFile = "c:\windows\system32\drivers\etc\hosts"
  string destFile = System.IO.Path.Combine(targetPath, newFileName);
  // destFile = "c:\windows\system32\drivers\etc\hosts.bak"

  if (!System.IO.Directory.Exists(targetPath))
  {
    System.IO.Directory.CreateDirectory(targetPath);
  }

  System.IO.File.Copy(sourceFile, destFile, true); // First File.Copy() call
  // File "c:\windows\system32\drivers\etc\hosts.bak" is created as a 
  // copy of "c:\windows\system32\drivers\etc\hosts" if either UAC is
  // disabled or the application is run as Administrator.
  // Otherwise "UnauthorizedAccessException - Access to path denied" is thrown

  if (System.IO.Directory.Exists(sourcePath))
  {
    fileName = System.IO.Path.GetFileName(sourcePath); // Setting of fileName is not used in your code again, is this intended or a mistake?
    // fileName = "etc" (Since the value of sourcePath is "c:\windows\system32\drivers\etc", GetFileName() sees the "etc" part as the FileName.
    // Should this not have been GetFileName(sourceFile) ??
    destFile = System.IO.Path.Combine(targetPath, newFileName);
    // destFile = "c:\windows\system32\drivers\etc\hosts.bak"
    System.IO.File.Copy(sourcePath, destFile, true); // Second File.Copy() call
    // This is where your exception happens since you are trying to copy
    // the file "etc" (which is actually a folder)
  }
  else
  {
    Console.WriteLine("Source path does not exist!");
  }
}

您看到“hosts.bak”文件的原因是您执行的第一次File.Copy()调用。由于正在创建文件，因此我必须假设您在环境中禁用了UAC，或者您的Visual Studio始终以管理员身份运行。

有关调试和单步执行代码的更多信息，请访问here

'System.UnauthorizedAccessException'但仍在复制文件

1 个答案: