How can I display a MessageBox when a website being searched is blocked by host?

[Modulus]

I have an application which adds text to the hosts file from a .txt file full of blacklisted websites.


It works, however, when the website is blocked, I want a Message to come up saying "Website Blocked". This is my code:

 Public Function Initizalize() As String
        Dim systemroot As String
        Dim root As String
        systemroot = Environment.GetEnvironmentVariable("SystemRoot")
        root = (systemroot + "\system32\drivers\etc\hosts")
        Return root
    End Function

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim dir As String
        dir = Me.Initizalize
        Dim systemroot As String
        Dim root As String
        systemroot = Environment.GetEnvironmentVariable("SystemRoot")
        root = (systemroot + "\system32\drivers\etc\hosts")
        Dim line As String
        Dim sr = New StreamReader("whitelistsites.txt")
        line = sr.ReadLine
        Dim filePath = "C:\Windows\System32\drivers\etc\hosts"

        File.WriteAllLines(filePath, File.ReadAllLines(filePath).Where(Function(s) s <> line))
        File.AppendAllText(dir, (Environment.NewLine _
                        + (line + Environment.NewLine)))

        While ((Not (line) Is Nothing) _
                    AndAlso (line <> ""))
            MessageBox.Show(("Appeanding Line: " + line))
            File.AppendAllText(dir, (line + Environment.NewLine))
            line = sr.ReadLine

        End While

        sr.Close()
        MessageBox.Show("Done!")
    End Sub

So, what I'm trying to say, is that when a website is searched [EDITED]FROM[/EDITED] the host file, it goes to the

ERR_CONNECTION_REFUSED

page on Chrome, then, once it goes to that page, I want a MessageBox to appear. Is there a way to do this?

I know, I've mentioned the Initialize code twice, but, I'm just going to leave it. Please comment for any more info. I didn't explain this very well, I know.

Maybe Google provides an API to do this? But what about for ALL browsers?

[si_the_geek]

I have no idea on your actual question, and I doubt it is possible (because you aren't involved in the actual blocking at all). There may be some API for chrome (or some other way of detecting that it has gone to that page) or even a Windows API to detect the issue, but I haven't heard of anything like it.

I know, I've mentioned the Initialize code twice, but, I'm just going to leave it. Please comment for any more info. I didn't explain this very well, I know.

Not only have you 'mentioned' it twice (never a good sign), but you also don't make use of it at all.

It would be better to write it like this:

    Public Function GetHostsPath() As String
        Dim systemroot As String
        Dim root As String
        systemroot = Environment.GetEnvironmentVariable("SystemRoot")
        root = (systemroot & "\system32\drivers\etc\hosts")
        Return root
    End Function

(the name describes what it does, and the & is what you should always use to join strings together, because + does strange things in some situations)

...and then to use it, instead of this:

        Dim filePath = "C:\Windows\System32\drivers\etc\hosts"

...do this:

        Dim filePath = GetHostsPath

[Modulus]

Ok, thanks for the tip.


Quick question, how do anti-viruses abort connections to malware sites and then show a message? This is what I'm trying to accomplish. See with Avast how they block website connections and then show the threat message, how do you do that?

[si_the_geek]

I would assume that anti-viruses do it by including a full firewall within their application, and when an attempt is made to visit a blacklisted site, they report that the connection was aborted (to the user and/or the application) and/or instead of getting data from the site simply return their own HTML for a web page that shows an "aborted" type message.

A firewall isn't something that is wise to write until you have a lot of experience, because even minor mistakes can cause big problems, including making the internet painfully slow (and some sites that use ajax wont return as much data, so you'll see less), or even disabling internet access until Windows is re-installed.

[Modulus]

Ok, right.

I've actually found something which may help me. Gonna test it outt: https://stackoverflow.com/questions/...lay-error-page

[si_the_geek]

I had a few minutes to spare, so I made some edits to the code you posted in #1 to reduce various problems:

    Public Function GetHostsPath() As String
        Dim systemroot As String
        Dim root As String
        systemroot = Environment.GetEnvironmentVariable("SystemRoot")
        root = (systemroot & "\system32\drivers\etc\hosts")
        Return root
    End Function

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim sr = New StreamReader("a full path here!\whitelistsites.txt")
        Dim line As String 
        Dim filePath = GetHostsPath

        line = sr.ReadLine
        File.WriteAllLines(filePath, File.ReadAllLines(filePath).Where(Function(s) s <> line))

        While (Not line Is Nothing) _
                    AndAlso (line <> "")
            MessageBox.Show("Appeanding Line: " & line)
            File.AppendAllText(filePath, Environment.NewLine & line)
            line = sr.ReadLine
        End While

        sr.Close()
        MessageBox.Show("Done!")
    End Sub

In addition to fixing the things I mentioned in post #2, this has eliminated lots of unnecessary brackets (the ones remaining on the While loop are a sensible style choice, and seems to be yours), highlighted an issue with the first file location (without a full path you are relying on luck to get the file you wanted), and eliminated one source of duplication you are causing in the hosts file (you were adding a line before the While loop, then adding the same line again inside the loop).

I also reduced the amount of new lines added to the hosts file, because your program would add extra blank lines every time it ran. If you particularly want the extra blank lines, append just a blank line (either before or after the loop).

This also doesn't eliminate most of the duplication you are causing, because you aren't doing what I recommended in your previous thread, which is to avoid writing duplicates in the first place: http://www.vbforums.com/showthread.p...t=#post5307033
The WriteAllLines/ReadAllLines method you are using is a very poor alternative, and still would be even if you hadn't made a mistake (which I wont clarify, because I don't want to help you continue with bad code).