C#•6mo ago

How to use C# to determine the end or next redirection point of a page

20 Replies

SpReeD•6mo ago

$details

MODiX•6mo ago

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Pobiega•6mo ago

What is a page? What is a redirection point? What is "end"? what is "next" (in this context)?

godlessOP•6mo ago

while (sheet.Cell(i, 0).ToString() != "")
{
    string t = sheet.Cell(i, 0).ToString();
    
    try
    {
        HTML = await client.GetStringAsync(sheet.Cell(i, 0).ToString());
    }
    catch (HttpRequestException e)
    {
        i++;
        continue;
    }
    finally
    {
        if (HTML != null)
        {
            if (HTML.Contains("googletagmanager.com") || HTML.Contains("google-analytics.com"))
            {
                sheet.Cell(i, Write - 1).Value = "1";
            }
            else
            {
                sheet.Cell(i, Write - 1).Value = "0";
            }
        }
        //here i nedd to save end URL after redirectings (if there was redirectings)
        i++;
    }
}

SpReeD•6mo ago

That's the point, are we talking about a Web-Page, an Excel-Sheet, a WPF-Page, a physical page on the scanner?

Pobiega•6mo ago

so uh.. you're fetching all the html from a webpage and storing it in... an excel cell?

godlessOP•6mo ago

if i get to site it may redirect me to another URL and if there was a redirection, i need to have a redirection URL

Pobiega•6mo ago

Ah okay, now I understand

godlessOP•6mo ago

i have an excel file where i have URL's and i need to check for some things

Pobiega•6mo ago

what kinda urls is this? and what are you checking for?

godlessOP•6mo ago

any urls just some sites now i nedd to find end URL

Pobiega•6mo ago

more info "any urls, just some sites" makes me think you are doing something malicious

godlessOP•6mo ago

i am watching sites that have links to my site to watch google analysis

Pobiega•6mo ago

hm... seems weird, but okay. I'll play ball for now. https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpclienthandler.allowautoredirect?view=net-8.0 first, we look at this property turns out HttpClient already follows redirection responses for you it does not follow meta header locations, or javascript redirects also, that code you run in finally is a bit weird imagine you query the url for i == 2 it fails. you then increase i by 1, so its now 3. then the finally block hits HTML might still contain the valid html from i == 1 but i is now 3, so the code does the wrong thing

godlessOP•6mo ago

yeah, i see

Pobiega•6mo ago

finally will run after the try or the catch, but it always runs you cant short circuit out of it so remove the finally, clear HTML in your catch, and remove the i++; continue;

var i = 1;
var httpClient = new HttpClient();

while (i < 1000)
{
    string? html = null;
    try
    {
        html = await httpClient.GetStringAsync(...);
    }
    catch (HttpRequestException)
    {
        html = null;
    }
    
    if (html != null)
    {
        // hey it worked, do stuff here.
    }

    i++;
}

var i = 1;
var httpClient = new HttpClient();

while (i < 1000)
{
    string? html = null;
    try
    {
        html = await httpClient.GetStringAsync(...);
    }
    catch (HttpRequestException)
    {
        html = null;
    }
    
    if (html != null)
    {
        // hey it worked, do stuff here.
    }

    i++;
}

godlessOP•6mo ago

so how can i see end url

Pobiega•6mo ago

probably can't when using GetStringAsync

godlessOP•6mo ago

how can i do it w/o using it? i was tryin to do this for 30 mins already

Pobiega•6mo ago

give this a try?

try
{
    var response = await httpClient.GetAsync("hello");
    if (response.IsSuccessStatusCode)
    {
        html = await response.Content.ReadAsStringAsync();
        var finalUrl = response.Headers.Location;
    }
}

try
{
    var response = await httpClient.GetAsync("hello");
    if (response.IsSuccessStatusCode)
    {
        html = await response.Content.ReadAsStringAsync();
        var finalUrl = response.Headers.Location;
    }
}

hello would be your URL, obviously so here we get the actual http response object instead of just the content we then check the location header from the response to determine the url we landed on this is untested, I just wrote it up quickly

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How to use C# to determine the end or next redirection point of a page