Setting Windows file security

Question

My problem is the opposite that most people have. I\'m generating files locally in C#, but I want them to be marked as blocked. So when a user opens them in an app

Answer 1

You need to write the alternate data stream yourself.

To do this, open the file with CreateFile and write the text using FileStream. Here is a simple exemple that works (tried on my computer).

[DllImport("kernel32", CharSet = CharSet.Unicode, SetLastError = true)] 
private static extern SafeFileHandle CreateFile(
string name, FileAccess access, FileShare share,
IntPtr security,
FileMode mode, FileAttributes flags,
IntPtr template);

    public static void Main()
    {
        // Opens the ":Zone.Identifier" alternate data stream that blocks the file
        using (SafeFileHandle handle = CreateFile(@"\\?\C:\Temp\a.txt:Zone.Identifier", FileAccess.ReadWrite, FileShare.None, IntPtr.Zero, FileMode.OpenOrCreate, FileAttributes.Normal, IntPtr.Zero))
        {
            // Here add test of CreateFile return code
            // Then :

            using (StreamWriter writer = new StreamWriter(new FileStream(handle, FileAccess.ReadWrite), Encoding.ASCII))
            {
                writer.WriteLine("[ZoneTransfer]");
                writer.WriteLine("ZoneId=3");
            }
        }