Grant file acceso to Everyone

gistfile1.cs

private static void GrantAccess(string filepath)
{
    // Get "Everyone" account name
    var sid = new SecurityIdentifier(WellKnownSidType.WorldSid, null);
    var acct = sid.Translate(typeof(NTAccount)) as NTAccount;
    var everyoneAccountName = acct.ToString(); // SP=Todos, EN=Everyone, FR...
    
    try
    {
        var infoFile = new FileInfo(filepath);
        
        // Create file if it does not exists yet
        if (!infoFile.Exists)
            infoFile.Create();

        var fileAccesoControl = infoFile.GetAccessControl();

        fileAccessControl.AddAccessRule(
            new FileSystemAccessRule(
                everyoneAccountName,
                FileSystemRights.FullControl,
                AccessControlType.Allow
                )
            );

        infoFile.SetAccessControl(fileAccessControl);
    }
    catch (Exception)
    { }
    finally
    {
        sid = null; acct = null;
    }
}