Unblock File from within .net 4 c#

Question

Is there a possibility to unblock a file that is downloaded from the internet from within a c# program. Surfing the internet I have learned, that the information is written in an alternative stream of a (NTFS) file that contains the current zone information (value 3 is from the internet and is interpreted as blocked).

Is there a managed possiblity to either clear or change the zone information (unblock) of a file or is there a managed copy function that copies the files without the zone information? If not, how can I do with PInvoke but without including a foreign assembly (I'm not allowed to do this in a current project).

@Sven: Thanks: I thought that I have exactly this written in my question. Is my english so bad? But thanks anyway... :) — HCL, Jun 16 '11 at 15:49
No, apparently my reading skills are, though. :) In my defense, it's after midnight here. Fwiw, you'll have to use PInvoke, as the .Net System.IO classes don't support alternate data streams. — Sven, Jun 16 '11 at 15:50
See http://stackoverflow.com/questions/604960/ntfs-alternate-data-streams-net — stuartd, Jun 16 '11 at 15:55

score 42 · Answer 1 · edited May 23 '17 at 11:46

Based on your input I have done the following code:

public class FileUnblocker {
    [DllImport("kernel32", CharSet = CharSet.Unicode, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool DeleteFile(string name);

    public bool Unblock(string fileName) {
        return DeleteFile(fileName + ":Zone.Identifier");
    }
}

Thanks to Stuart Dunkeld, Alex K(+1) and Sven to show me the direction.

UPDATE I have posted the code here for a feedback if it would work reliable in production environment. If someone want to use it, check out there.

Updates like this should be posted as an edit to your question. — Sam Axe, Jul 27 '15 at 22:56

score 21 · Accepted Answer · answered Jun 16 '11 at 15:58

21

It's stored in the :Zone.Identifier stream (more < c:\theapp.exe:Zone.Identifier) you need to use the native IO routines to manipulate them, here is a managed wrapper.

answered Jun 16 '11 at 15:58

Alex K.

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4

While this may work for now, it is an implementation detail. The [Persistent Zone Identifier object](https://msdn.microsoft.com/en-us/library/ms537029(v=vs.85).aspx), as mentioned by @citizenmatt, is the bit responsible for creating these. As such, MS may at any time, via Windows update or OS version, change how/where that data is stored. – Sam Axe Jul 27 '15 at 22:59

score 6 · Answer 3 · answered Jul 19 '12 at 09:06

6

The official way to manage this identifier is with the PersistentZoneIdentifier COM object: http://msdn.microsoft.com/en-us/library/ms537029(v=vs.85).aspx

answered Jul 19 '12 at 09:06

citizenmatt

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score 0 · Answer 4 · answered Mar 14 '23 at 16:31

0

If all you want is to unblock files use a powershell command:

dir -r | unblock-files

change directory to the folder containing the files and run that command. The parameter -r is to list files in all sub-folders.

answered Mar 14 '23 at 16:31

D. Kermott

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score 0 · Answer 5 · answered Jun 29 '23 at 05:09

I'm using .net 7, I've found these does the same thing.

Unblock:

void UnblockFile(string filePath)
{
    File.Delete(filePath + ":Zone.Identifier");
}

Block:

void BlockFile(string filePath)
{
    File.WriteAllText(filePath + ":Zone.Identifier", "[ZoneTransfer]\r\nZoneId=3");
}

Unblock File from within .net 4 c#

5 Answers5

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