How do I force a maximum pathlength with more than 260 characters

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Hello everyone,

I have a problem with saving. I need to images which path's are longer than the 260 characters (Sadly they have to be this long. Not my idea!)

I found this one here:
[^]

I tried the \\?\ but it didn't work.

My path is: "\\?\D:\Temp1\Data\"
In this case Visual Studio says that there is an unknown escape sequence.

Then i tried @"\\?\D:\Temp1\Data"
Visual Studio says that there is a sign which is not allowed. I guess it is the "?"

And when I try it without the \\?\ there is the windows exception which says that the Path only allows 260 characters.

What mistake/s did i do?

I hope you can help me.

Best regards
Richard

What I have tried:

These links:
https://blogs.msdn.microsoft.com/bclteam/2007/03/26/long-paths-in-net-part-2-of-3-long-path-workarounds-kim-hamilton/

https://msdn.microsoft.com/en-us/library/aa365247.aspx

Posted 27-Jun-16 1:12am

Evosoul04

Updated 27-Jun-16 5:57am

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[no name] 27-Jun-16 7:22am

"\\?\" means computer name. Example : \\server1\publicshare
Example : File.Delete(@"D:\Temp1\Data\file1.txt"):

Evosoul04 27-Jun-16 7:32am

In the MSDN example it is said, that I should use the \\?\ when I have a path which is longer than 260 characters. Or am I mistaken here? https://msdn.microsoft.com/en-us/library/aa365247.aspx#maxpath

Dave Kreskowiak 27-Jun-16 8:33am

If you're trying to use the classes and methods built into the .NET Framework System.Io namespace they're not going to work with longer than normal filepaths.

You have to do what you linked to and write you're own methods to handle the basic file operations.

Without seeing your code it's impossible to tell you what you did wrong.

johannesnestler 27-Jun-16 10:24am

I tested the exact Code from the blog example OP linked - it didn't work, even with the PInvoke calls instead of System.IO...

Dave Kreskowiak 27-Jun-16 11:01am

I can't test it for you right now. I don't have VS installed yet from a system rebuild and I don't have the time.

Richard MacCutchan 27-Jun-16 12:00pm

Code sample works as documented.

[no name] 27-Jun-16 11:14am

With PInvoke, did you make sure to use the Unicode ("W") Versions?

Developers Reverence:
Windows NT: You can use paths longer than MAX_PATH characters by calling the wide (W) version of CreateFile and prepending "\\?\" to the path. The "\\?\" tells the function to turn off path parsing. This lets you use paths that are nearly 32,000 Unicode characters long. You must use fully-qualified paths with this technique. This also works with UNC names. The "\\?\" is ignored as part of the path. For example, "\\?\C:\myworld\private" is seen as "C:\myworld\private", and "\\?\UNC\tom_1\hotstuff\coolapps" is seen as "\\tom_1\hotstuff\coolapps".

Richard Deeming 27-Jun-16 15:00pm

Rather than trying to write the code yourself, why not use a pre-built library to do the job for you:
Zeta Long Paths[^] by Uwe Keim has been around for nearly seven years, and seems to work well.

Alternatively, change the requirements so that you don't try to break Windows! :)

Richard MacCutchan 27-Jun-16 17:49pm

See my solution below, nothing broken.

2 solutions

Solution 1

Hi Evosoul04,

Sadly I can offer no real help for your problem. But at least I tried to follow the steps from your linked blog article. I copied the code to a little test project. But I observed the same behavior like you - it didn't work (System can not find the path specified), But I think it did everything correct according to: Naming Files, Paths, and Namespaces (Windows)[^]
So at least you can say: others had the same Problem ;) - It seems to me that we miss some important information here to get this working (or Microsoft changed the behavior in between -who knows?)

Greetings from Austria
Johannes

Posted 27-Jun-16 4:16am

johannesnestler

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Richard MacCutchan 27-Jun-16 11:58am

See my solution below.

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Richard MacCutchan · Accepted Answer · 2016-06-27T05:57:00

Solution 2

I used the code in the link you provided and it worked as expected. Please edit your question and show the exact code you are using so we can see what is different.

[edit]
The following code works:

C#

[DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
[return: MarshalAs(UnmanagedType.Bool)]
internal static extern bool DeleteFile(string lpFileName);

public static void Delete(string fileName)
{
    string formattedName = @"\\?\D:\Temp\" + fileName;
    DeleteFile(formattedName);
}

[/edit]

Posted 27-Jun-16 5:57am

Richard MacCutchan

Updated 27-Jun-16 6:13am

v2

Comments

[no name] 27-Jun-16 18:12pm

Also if path is more than 260 chars? Only a question...

Richard MacCutchan 28-Jun-16 4:05am

Don't have any paths that long to test.

Evosoul04 28-Jun-16 1:50am

Thanks this worked. BUt i found a "better" solution in my opinion. I use the "Zeta Long Path NuGet package". It also imports the kernel32.dll.