检查文件夹是否存在的问题

Question

I have the following C# code that creates a folder:

if (!Directory.Exists(strCreatePath))
{
    Directory.CreateDirectory(strCreatePath);
}

It works, except if I have a folder as such: C:\\\\Users\\\\UserName\\\\Desktop the Directory.Exists returns false , which is not true, but then Directory.CreateDirectory throws an exception: Access to the path 'C:\\\\Users\\\\UserName\\\\Desktop' is denied. .

Any idea how to prevent that apart from catching such exception, which I prefer to avoid?

Answer 1

According to the docs :

If you do not have at a minimum read-only permission to the directory, the Exists method will return false.

So the behavior you are seeing is expected. This is a legitimate exception that can happen even if you do check for permissions, so your best bet is to simply handle the exception.

Answer 2

You should check first if the directory is ReadOnly or not:

bool isReadOnly = ((File.GetAttributes(strCreatePath) & FileAttributes.ReadOnly) == FileAttributes.ReadOnly);
if(!isReadOnly)
{
    try
    {
         Directory.CreateDirectory(strCreatePath);
    } catch (System.UnauthorizedAccessException unauthEx)
    {
        // still the same eception ?!
        Console.Write(unauthEx.ToString());
    }
    catch (System.IO.IOException ex)
    {
        Console.Write(ex.ToString());
    }
}

Answer 3

Thank you, everyone. Here's how I was able to handle it without throwing unnecessary exceptions:

[DllImportAttribute("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool CreateDirectory(string lpPathName, IntPtr lpSecurityAttributes);

void createFolder(string strCreatePath)
{
    if (!CreateDirectory(strCreate, IntPtr.Zero))
    {
        int nOSError = Marshal.GetLastWin32Error();
        if (nOSError != 183)        //ERROR_ALREADY_EXISTS
        {
            //Error
            throw new System.ComponentModel.Win32Exception(nOSError);
        }
    }
}