CODEWITHSUNDEEP
c#htmlsubstring
CSharper
CSharper

Reputation: 3

Get substring in C# from the html?

I have a page where I need to get the substring so I made this code :

static string GetBetween(string message, string start, string end)
        {
            int startIndex = message.IndexOf(start) + start.Length;
            int stopIndex = message.IndexOf(end);
            return message.Substring(startIndex, stopIndex - startIndex);

        }

And this is the code that gets the value: 

 string myStr = HttpMethods.Get("https://www.marktplaats.nl/account/login.html", "https://www.marktplaats.nl/account/login.html", ref myCookies);
            string myToken;
            Console.WriteLine("Token: " + (myToken = GetBetween(myStr, "name='xsrf.token' value='", "'>")));

But instead of getting the value between this line (The value changes every time I do a new WebRequest so I need to get the new value every time):

<input type="hidden" name="xsrf.token" value="1576329716873.d7a4f9a4b3f8e63fa5d1fe94730774c34b327ec96cdbb4aaca405de3b96231b3(THIS CHANGES EVERYTIME I LOAD THE PAGE)">

It gives me this output:

ng="nl">
<head>
    <title>= Marktplaats - De plek om nieuwe en tweedehands spullen te kopen en verkopen</title>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <meta http-equiv="Content-Language" content="nl">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta name="description" content="De grootste advertentiesite van Nederland. Nieuwe en tweedehands goederen en diensten, koopt en verkoopt u op Marktplaats.nl.">
    <link rel="shortcut icon" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/favicon.3e02874c.ico">
    <link rel="apple-touch-icon" sizes="57x57" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/apple-touch-icon-57x57.722d5557.png">
    <link rel="apple-touch-icon" sizes="114x114" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/apple-touch-icon-114x114.fdd2bafc.png">
    <link rel="apple-touch-icon" sizes="72x72" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/apple-touch-icon-72x72.6af4f862.png">
    <link rel="apple-touch-icon" sizes="144x144" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/apple-touch-icon-144x144.319efd6c.png">
    <link rel="apple-touch-icon" sizes="60x60" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/apple-touch-icon-60x60.c37547f0.png">
    <link rel="apple-touch-icon" sizes="120x120" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/apple-touch-icon-120x120.94703796.png">
    <link rel="apple-touch-icon" sizes="76x76" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/apple-touch-icon-76x76.8866913d.png">
    <link rel="apple-touch-icon" sizes="152x152" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/apple-touch-icon-152x152.d5085224.png">
    <link rel="apple-touch-icon" sizes="180x180" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/apple-touch-icon-180x180.8a15fd8d.png">
    <link rel="icon" type="image/png" sizes="192x192" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/favicon-192x192.da693c37.png">
    <link rel="icon" type="image/png" sizes="160x160" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/favicon-160x160.a3b4d12c.png">
    <link rel="icon" type="image/png" sizes="96x96" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/favicon-96x96.cc0ba841.png">
    <link rel="icon" type="image/png" sizes="16x16" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/favicon-16x16.ce3b2c65.png">
    <link rel="icon" type="image/png" sizes="32x32" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/favicon-32x32.595f2e60.png">
    <meta name="theme-color" content="#eda566">
    <meta name="msapplication-TileColor" content="#eda566">
    <meta name="msapplication-square150x150logo" content="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/mstile-150x150.e3e83679.png">
    <meta name="msapplication-square310x310logo" content="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/mstile-310x310.09da1373.png">
    <meta name="msapplication-square70x70logo" content="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/mstile-70x70.2bc50495.png">
    <meta name="msapplication-wide310x150logo" content="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/favicons/mstile-310x150.80f61dab.png">
    <meta name="msapplication-config" content="none">
    <meta name="generation-time-millis" content="1576332442585">
    <meta name="user-logged-in" content="false">
    <link rel="stylesheet" type="text/css" href="//s.marktplaats.com/static-web/identity/vendor/normalize.css/normalize.112272e5.css" />
    <link rel="stylesheet" type="text/css" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/Index.ad7c2c53.css" />

        <script src="//s.marktplaats.com/static-web/identity/vendor/design-sdk/polyfills/polyfills.bce7e2b1.js"></script>
        <script src="//s.marktplaats.com/static-web/identity/vendor/design-sdk/components/polymer.1a8b099b.js"></script>
        <link rel="import" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/themes/mp/CssVars.d3ec1e54.html">
        <style is="custom-style" include="mp-css-vars"></style>
        <link rel="import" href="//s.marktplaats.com/static-web/identity/vendor/design-sdk/organisms/header.63727d14.html">
        <link rel="stylesheet" type="text/css" media="screen" href="//s.marktplaats.com/static-web/identity/css/Login.mp.nlnl.6f8ceda7.css"/>
    <script>
        window.dataLayer = [{"p":{"t":"Login"},"c":{"l1":{"id":-1},"l2":{"id":-1},"c":{"id":-1}},"u":{"li":false,"tg":{"stg":"aur7110_b|aur10242_a|aur6493_a|aur9628_b|aur3815-android_b|alternative-redirect_b|aur9245_a|aur9234_b|aur7712new_c|aur9777_c|aur9214_b|aur7342android_c|an-lmap_b|aur9848_b|aur9247_b|aur7377-order_b|aur8977_c|aur2445_b|aur9583_b|aur10018_a|aur9439_b|aur8030_c|aur2389_s_b|aur5496_a|vos2-150_b|aur7892_b|aur9856_b|aur9629_a|aur9007_b|vos6677_b|aur9752_a|aur10141_a|aur6760_a|aur-cdata345_a|aur10256_a|aur8865_b|aur4923_c|aur6594_a|aur5875_c|aur-cdata673_b|aur7918_b|aur3815_s_b|aur9834_b|aur8682_b|aur9749_a|aur6087_b|aur6503_a|aur8949_a|aur8950_a|aur9863_c|aur8221_b|aur8863_b|aur8808_b|aur5346_b|aur9685_b|aur8722_c|aur9555_b|pie3083-vip_a|aur6745_a|pie-2608-reblaze-challenge-tag_a|aur4627_b|aur10388_b|aur8790_b|aur8721_c|aur6916_a|aur9761_a|unsupported-browser-warning_b|aur3130_b|aur7826_b|aur9996_b|aur7464_b|aur9939_b|aur2389_v_b|aur5496-android_a|aur7958_b|aur10124_b|aur6034_a|aur2862_b|aur8869_b|aur9380_b|aur3186_b|aur8533_b|aur6207_b|aur9287v2_b|aur6768_b|aur9714_b|aur6915_a|aur10022_b|aur9187_b|aur10313_a|aur2805_b"}},"d":{"ua":"Go-http-client\u002F1.1"},"s":{"pn":-1,"ps":-1,"tr":-1,"srt":{},"prc":{"mn":-1,"mx":-1}},"l":{"d":-1},"a":{},"o":{},"m":{}}];
    </script>

        <script src="//s.marktplaats.com/static-web/identity/vendor/raven-js/raven.min.daf037c2.js" crossorigin="anonymous"></script>
        <script type="text/javascript">
            Raven.config('https://[email protected]/10', {
                release: 'nohash',
                tags: {
                    artifactId: 'identity-frontend',
                    requestId: '998712b4-8022-47fb-bcc6-d18f0c4de521'
                }
            }).install();

        </script>

    <script type='text/javascript

The website is:

https://www.marktplaats.nl/account/login.html

After this error was fixed I got this one this is my whole webrequest:

This is my method

This is my main program.cs

Upvotes: 0

Views: 1089

Answers (3)

Jim Berg
Jim Berg

Reputation: 659

Your call to GetBetween doesn't even pass the correct values. It should be a double-quote, not a single quote since the text you're searching uses double quotes.

You also need verify that you actually find the string by checking if the index is less than zero.

You can use this:

    public static string GetBetween(string source, string start, string end)
    {
        var startPos = source.IndexOf(start, StringComparison.Ordinal);
        if (startPos < 0) return null;
        startPos += start.Length;
        var endPos = source.IndexOf(end, startPos,StringComparison.Ordinal);
        return endPos < 0 ? null : source.Substring(startPos, endPos - startPos - 1);
    }

I return null if the string isn't present.

Adding Benchmark Code for reference: private static string check = "";

    static void Main(string[] args)
    {
        string regex = "<input type\\=\\\"hidden\\\" name=\\\"xsrf\\.token\\\" value\\=\\\"([^\\\"]+)\\\"";
        var reg = new Regex(regex);
        string xsrfToken;
        DateTime start;
        TimeSpan diff;
        var rnd = new Random();

        for (var j = 0; j < 100; j++)
        {
            if (rnd.Next(30) < 10)
            {
                start = DateTime.Now;
                for (var i = 0; i < 10000000; i++)
                    xsrfToken = Regex.Match(check, regex).Groups[1].Value;
                diff = DateTime.Now - start;
                Console.WriteLine("RegEx: " + diff.TotalSeconds);
                continue;
            }

            if (rnd.Next(30) < 20)
            {
                start = DateTime.Now;
                for (var i = 0; i < 10000000; i++)
                    xsrfToken = reg.Match(check).Groups[1].Value;
                diff = DateTime.Now - start;
                Console.WriteLine("RegEx Prepped: " + diff.TotalSeconds);
                continue;
            }

            start = DateTime.Now;
            for (var i = 0; i < 10000000; i++)
                xsrfToken = InBetween(check, "name=\"xsrf.token\" value=\"", ">");
            diff = DateTime.Now - start;
            Console.WriteLine("InBetween: " + diff.TotalSeconds);
        }

        Console.ReadKey();
    }

    public static string InBetween(string source, string start, string end)
    {
        var startPos = source.IndexOf(start, StringComparison.Ordinal);
        if (startPos < 0) return null;
        startPos += start.Length;
        var endPos = source.IndexOf(end, startPos, StringComparison.Ordinal);
        return endPos < 0 ? null : source.Substring(startPos, endPos - startPos - 1);
    }

Upvotes: 0

Aydin
Aydin

Reputation: 15284

Use regex.

string myStr = HttpMethods.Get("https://www.marktplaats.nl/account/login.html", "https://www.marktplaats.nl/account/login.html", ref myCookies);
string regex = "<input type\\=\\\"hidden\\\" name=\\\"xsrf\\.token\\\" value\\=\\\"([^\\\"]+)\\\"";

var xsrfToken = Regex.Match(myStr, regex).Groups[1].Value;

Console.WriteLine(xsrfToken);

As for those stating you should never use Regex for parsing HTML, using HTML Agility Pack for something like this is overkill and will likely perform a lot worse too, don't believe me? Hear it from their own developers

https://html-agility-pack.net/knowledge-base/43677736/csharp-htmlagilitypack-vs-regular-expressions-for-extracting-links-from-html

Upvotes: 1

JFoxx64
JFoxx64

Reputation: 262

If string start = 

"name=\"xsrf.token\" value=\""

and string end = 

"\""

Then:

static string GetBetween(string message, string start, string end)
        {
            //Required to handle possible problems that will arise due to indexing if the string does not exist
            try{

                //Splits the original message by the character array of the string "start", then takes the second index of that string array
                string splitmessage = message.Split(new string[] {start})[1]

                //Splits the remaining message by the character array of string "end", then takes the first index of that string array
                splitmessage = message.Split(new string[] {end})[0]

                return splitmessage;

            } catch(Exeption ex){
                //Handle when the string you're attempting to find is not there
            }

        }

Should return only the value of the input you are looking for.

You will have to handle what happens when that value is not found separately.

Upvotes: 0

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