Find indexes in String using multiple search items and one single iteration

Question

I have the following HTML sample document:

.....
<div class="TableElement">
    <table>
    <tr>
        <th class="boxToolTip" title="La quotazione di A2A è in rialzo o in ribasso?">&nbsp;</th>
        ..
        <th class="boxToolTip" class="ColumnLast" title="Trades più recenti su A2A">Ora <img title='' alt='' class='quotePageRTupgradeLink' href='#quotePageRTupgradeContainer' id='cautionImageEnt' src='/common/images/icons/caution_sign.gif'/></th>
    </tr>
    <tr class="odd">
        ..
        <td align="center"><span id="quoteElementPiece6" class="PriceTextUp">1,619</span></td>
        <td align="center"><span id="quoteElementPiece7" class="">1,6235</span></td>
        <td align="center"><span id="quoteElementPiece8" class="">1,591</span></td>
        <td align="center"><span id="quoteElementPiece9" class="">1,5995</span></td>
        ..
    </tr>
    </table>
</div>
......

I need to get the values corresponding at quoteElementPiece 6,7,8,9 and 17 (currently further in the document) section.

I am simply searching one by one in the code at the moment:

int index6 = doc.IndexOf("quoteElementPiece6");
..
int index17 = doc.IndexOf("quoteElementPiece17");

I want to improve this by scanning in one go and having all the indexes for the substrings I need. Example:

var searchstrings = new string[]
{
    "quoteElementPiece6",
    "quoteElementPiece7",
    "quoteElementPiece8",
    "quoteElementPiece9",
    "quoteElementPiece17"
};

int[] indexes = getIndexes(document,searchstrings); //indexes should be sorted accordingly to the order in searchstrings

Is there anything native in .NET doing this (LinQ for istance)?

I know there are HTML Parser libraries but I prefer avoiding using those, I would like to learn how to do this for each kind of document.

Please show at least what you have googled?.... A simpler search gives this: [C# Is there a LINQ to HTML, or some other good .Net HTML manipulation API?](https://stackoverflow.com/q/542194/6400526) — Gilad Green, Dec 16 '18 at 19:12
I want to avoid using third party libraries or to parse the whole HTML, the document being an HTML is just an example. — farbiondriven, Dec 16 '18 at 19:14
You can use Linq To XML, but that requires a well formed HTML which you can get using SgmlReader. You might also use HtmlAgilityPack. — Cetin Basoz, Dec 16 '18 at 19:15

score 2 · Accepted Answer · answered Dec 16 '18 at 19:28

2

var words = new []{
    "quoteElementPiece6",
    "quoteElementPiece7"};      
// I take for granted your `document` is a string and not an `HtmlDocument` or whatnot.
var result = words.Select(word=>document.IndexOf(word));
Console.WriteLine(string.Join(",", result));

answered Dec 16 '18 at 19:28

LosManos

7,195
6
56
107

2

This works and it's more elegant. But it doesn't perform the scan in one go. – farbiondriven Dec 16 '18 at 20:32
Then I believe you should look into RegEx but then [you have two problems](https://en.wikiquote.org/wiki/Jamie_Zawinski). – LosManos Dec 16 '18 at 20:48

score 0 · Answer 2 · edited Dec 16 '18 at 19:29

0

you can do this with LINQ. check my solution

var doc = "this is my document";
List<string> searchstrings = new List<string>
{
    "quoteElementPiece6",
    "quoteElementPiece7",
    "quoteElementPiece8",
    "quoteElementPiece9",
    "quoteElementPiece17"
};
var lastIndexOfList = new List<int>(searchstrings.Count);

searchstrings.ForEach(x => lastIndexOfList.Add(doc.LastIndexOf(x)));

edited Dec 16 '18 at 19:29

LosManos

7,195
6
56
107

answered Dec 16 '18 at 19:28

Derviş Kayımbaşıoğlu

28,492
4
50
72

JohnyL · Answer 3 · 2018-12-17T05:18:11.053

0

var pattern = @"(?s)<tr class=""odd"">.+?</tr>";
var tr = Regex.Match(html, pattern).Value.Replace("&nbsp;", "");
var xml = XElement.Parse(tr);
var nums = xml
            .Descendants()
            .Where(n => (string)n.Attribute("id") != null)
            .Where(n => n.Attribute("id").Value.StartsWith("quoteElementPiece"))
            .Select(n => Regex.Match(n.Attribute("id").Value, "[0-9]+").Value);

edited Dec 17 '18 at 05:18

answered Dec 16 '18 at 19:43

JohnyL

6,894
3
22
41

it seems like you are looking for matching tags, but because the `+`is greedy, it does not have to be the case. – Antonín Lejsek Dec 16 '18 at 22:37

Find indexes in String using multiple search items and one single iteration

3 Answers3