.NET How to check if path is a file and not a directory?

Question

I have a path and I need to determine if it is a directory or file.

Is this the best way to determine if the path is a file?

string file = @"C:\Test\foo.txt";

bool isFile = !System.IO.Directory.Exists(file) && 
                         System.IO.File.Exists(file);

For a directory I would reverse the logic.

string directory = @"C:\Test";

bool isDirectory = System.IO.Directory.Exists(directory) && 
                            !System.IO.File.Exists(directory);

If both don't exists that then I won't go do either branch. So assume they both do exists.

Possible duplicate of Better way to check if a Path is a File or a Directory? — DavidRR
– DavidRR, Commented Sep 7, 2016 at 12:50

Alnitak · Accepted Answer · 2009-01-13 16:07:22Z

125

Use:

System.IO.File.GetAttributes(string path)

and check whether the returned FileAttributes result contains the value FileAttributes.Directory:

bool isDir = (File.GetAttributes(path) & FileAttributes.Directory)
                 == FileAttributes.Directory;

edited Jan 13, 2009 at 16:07

answered Jan 13, 2009 at 15:52

Alnitak

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6 Comments

LBushkin Over a year ago

Just make sure you do this in a try/catch, since the path may not even exist.

Michael Sheely Over a year ago

What happens if the path has wildcards in it? I get an illegal character argument, but what if I use wildcards and that's a legitimate path for my users?

ToolmakerSteve Over a year ago

@MichaelSheely - AFAIK, to deal with wildcards you have to call Directory.GetFiles with the string, and see whether the result has a count greater than zero. A "path with wildcards" isn't a path. It is a pattern.

IulianT Over a year ago

will not work if path(dir of file) does not exist

Alnitak Over a year ago

@LeresAldtai it is assumed that the path does exist - the OP didn't ask for a check that the path is non-existent.

|

M P · Accepted Answer · 2013-12-22 17:37:53Z

59

I think this is the simplest way where you only need two checks:

string file = @"C:\tmp";
if (System.IO.Directory.Exists(file))
{
    // do stuff when file is an existing directory
}
else if (System.IO.File.Exists(file))
{
    // do stuff when file is an existing file
}

edited Dec 22, 2013 at 17:37

M P

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answered Jan 13, 2009 at 16:00

Dirk Vollmar

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10 Comments

Christian.K Over a year ago

I did not downvote you, but it the accepted answer is surely "simpler" and only needs one call (not two).

Tao Over a year ago

The advantage of this approach is that it works even if there is no matching entry in the filesystem at all (in other words, it is neither a folder nor a file); In that sense, it is "simpler". Incidentally, the OP said "a path", and not "a path that is known to exist".

Ben Collins Over a year ago

Yeah, I actually think this is the better answer when you're not sure the path you're investigating is there or not. Not having to worry about catching exceptions is a big deal.

Synetech Over a year ago

I agree that this method is effective. I just created a tiny utility to identify whether the specified name is a file or directory and this method made it extremely simple to return 1 for directory, 2 for file, and 0 for error (e.g., the name is invalid). The tool is tiny (338 bytes source, 3584 bytes compiled) and runs very fast.

Dirk Vollmar Over a year ago

@TomPadilla: What exactly would you expect to happen if the path does not exist?

|

Scott Dorman · Accepted Answer · 2009-01-15 18:23:58Z

11

You can do this with some interop code:

    [DllImport("shlwapi.dll", CharSet = CharSet.Unicode)]
    [return: MarshalAsAttribute(UnmanagedType.Bool)]
    public static extern bool PathIsDirectory([MarshalAsAttribute(UnmanagedType.LPWStr), In] string pszPath);

To further clarify some of the comments...

Introducing unmanaged code in this is not any more inherintly dangerous than any of the other file or I/O related calls in .NET since they ultimatley all call in to unmanaged code.

This is a single function call using a string. You aren't introducing any new data types and/or memory usage by calling this function. Yes, you do need to rely on the unmanaged code to properly clean up, but you ultimately have that dependency on most of the I/O related calls.

For reference, here is the code to File.GetAttributes(string path) from Reflector:

public static FileAttributes GetAttributes(string path)
{
    string fullPathInternal = Path.GetFullPathInternal(path);
    new FileIOPermission(FileIOPermissionAccess.Read, new string[] { fullPathInternal }, false, false).Demand();
    Win32Native.WIN32_FILE_ATTRIBUTE_DATA data = new Win32Native.WIN32_FILE_ATTRIBUTE_DATA();
    int errorCode = FillAttributeInfo(fullPathInternal, ref data, false, true);
    if (errorCode != 0)
    {
        __Error.WinIOError(errorCode, fullPathInternal);
    }
    return (FileAttributes) data.fileAttributes;
}

As you can see, it is also calling in to unmanaged code in order to retrieve the file attributes, so the arguements about introducing unmanaged code being dangerous are invalid. Likewise, the argument about staying completely in managed code. There is no managed code implementation to do this. Even calling File.GetAttributes() as the other answers propose have the same "issues" of calling unmanged code and I believe this is the more reliable method to accomplish determining if a path is a directory.

Edit To answer the comment by @Christian K about CAS. I believe the only reason GetAttributes makes the security demand is because it needs to read the properties of the file so it wants to make sure the calling code has permission to do so. This is not the same as the underlying OS checks (if there are any). You can always create a wrapper function around the P/Invoke call to PathIsDirectory that also demands certain CAS permissions, if necessary.

edited Jan 15, 2009 at 18:23

answered Jan 13, 2009 at 15:50

Scott Dorman

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14 Comments

David Basarab Over a year ago

That seems like allot of work to figure out if a path is a file or directory.

Dirk Vollmar Over a year ago

I don't see why this is downvoted, although it would be much simpler to stay in managed code using .NET functionality only.

David Basarab Over a year ago

Introducing Unmanaged code to get if a path is a file or directory is dangerous. I have to relay on the calling function to clean up the memory properly or my code could have leaks.

Scott Dorman Over a year ago

I still fail to see why this is getting downvoted as it correctly answers the question with a method that provides no level of ambiguitity.

Wodzu Over a year ago

That is the "beauty" of SO, even a good answers might be downvoted by some zealots ;)

|

Dirk Vollmar · Accepted Answer · 2009-01-13 16:41:36Z

7

Assuming the directory exists...

bool isDir = (File.GetAttributes(path) & FileAttributes.Directory)
                  == FileAttributes.Directory;

edited Jan 13, 2009 at 16:41

Dirk Vollmar

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answered Jan 13, 2009 at 15:52

tvanfosson

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2 Comments

Binary Worrier Over a year ago

If path doesn't exist, GetAttributes will return -1.

tvanfosson Over a year ago

Docs seem to indicate that it will throw an exception if the file doesn't exist. msdn.microsoft.com/en-us/library/…

Dror · Accepted Answer · 2009-01-13 15:54:05Z

4

Check this out:

/// <summary>
/// Returns true if the given file path is a folder.
/// </summary>
/// <param name="Path">File path</param>
/// <returns>True if a folder</returns>
public bool IsFolder(string path)
{
    return ((File.GetAttributes(path) & FileAttributes.Directory) == FileAttributes.Directory);
}

from http://www.jonasjohn.de/snippets/csharp/is-folder.htm

answered Jan 13, 2009 at 15:54

Dror

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Comments

Igor Zelaya · Accepted Answer · 2009-01-13 15:54:42Z

2

Read the file attributes:

FileAttributes att = System.IO.File.GetAttributes(PATH_TO_FILE);

Check for the Directory flag.

answered Jan 13, 2009 at 15:54

Igor Zelaya

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Comments

Drew Noakes · Accepted Answer · 2009-01-13 15:55:43Z

1

Given that a particular path string cannot represent both a directory and a file, then the following works just fine and opens the door for other operations.

bool isFile = new FileInfo(path).Exists;
bool isDir = new DirectoryInfo(path).Exists;

If you're working with the file system, using FileInfo and DirectoryInfo is much simpler than using strings.

answered Jan 13, 2009 at 15:55

Drew Noakes

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2 Comments

nawfal Over a year ago

See 0xA3's answer, slightly better calls imo.

Chris Bordeman Over a year ago

Or just if (Directory.Exists(src)) ... If it's a file, it'll be false. If src is a directory, it'll be false. If src is a directory that doesn't exist, then by definition src can't a directory.

Jon7 · Accepted Answer · 2013-01-10 20:37:06Z

-4

Hmm, it looks like the Files class (in java.nio) actually has a static isDirectory method. So, I think you could actually use the following:

Path what = ...
boolean isDir = Files.isDirectory(what);

edited Jan 10, 2013 at 20:37

Jon7

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answered Jan 10, 2013 at 20:20

Onikoroshi

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David Basarab Over a year ago

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