Concatenate two Node Set with XPath

Question

Suppose I have this HTML file :

<html>
    <table class="class1">
        <tr>
            <td>1</td>
            <td>2</td>
        </tr>
        <tr>
            <td>1</td>
            <td>2</td>
        </tr>
    </table>

    <table class="class2">
        <tr>
            <td>a</td>
            <td>b</td>
            <td>c</td>
            <td>d</td>
            <td>e</td>
        </tr>
    </table>

    <table class="class3">
        <tr>
            <td>3</td>
            <td>4</td>
            <td>5</td>
        </tr>
        <tr>
            <td>3</td>
            <td>4</td>
            <td>5</td>
        </tr>
    </table>
</html>

I would like to query this file with XPath in order to get this result : 1234512345 with this code :

var xNavigator = xPathDoc.CreateNavigator();
var iterator = xNavigator.Select("//html/table[@class='class1']/tr/td|//html/table[@class='class3']/tr/td");
while (iterator.MoveNext())
    Console.Write(iterator.Current.InnerXml);

but the result is : 1212345345

Do you have any idea how can I get 1234512345 instead 1212345345 ?

Thank you.

I think I know what you want, but this example is ambiguous. Change it so that the table cells have unique values (maybe 1-4 for the class1 table, and A-F for the class3 table). Then describe what you want. — Michael Gunter, Jun 21 '13 at 15:00
I but it like that because every cell have it's own data(type : date maybe or specific values) ! but the number there is about to show you the need to have those data in order : all cells from table calss1 followed by all cells in table class2 again and again — Aladdin Gallas, Jun 21 '13 at 15:25
Note that `|` is not a concatenation operator, but a union operator. There is no node set concatenation operator in XPath 1.0 because sets have no defined ordering, so concatenation doesn't make sense. In order to keep track of a custom ordering, you need sequences, which require XPath 2.0. Or use the features of the C# environment, as @MichaelGunter suggested. — LarsH, Jun 21 '13 at 15:34

score 1 · Answer 1 · edited May 23 '17 at 12:20

1

I think you're going to need to perform two Selects. As described in the discussion below, XPath 1.0 (which is the only version .NET has support for) doesn't define node order, and the implementations all return the nodes in document order.

Returning XPath correct order ( insted of document order)

edited May 23 '17 at 12:20

Community

1
1

answered Jun 21 '13 at 15:06

Michael Gunter

12,528
1
24
58

I have to perform that in only one Select if it's possible. The question is not about the C# code but it's about the XPath ! :) – Aladdin Gallas Jun 21 '13 at 15:26
1

@AladdinGallas: and the answer to your question is that XPath is incapable of what you're asking, in a single Select. – LarsH Jun 21 '13 at 15:30

score 1 · Accepted Answer · answered Jun 21 '13 at 16:45

Since you're talking "node-sets" I assume you're using XPath 1.0 - you really ought to say so. A node-set in XPath 1.0 is a set of nodes with no particular order; however XSLT always processes the nodes in a node-set in document order, and this has established a precedent which as far as I know all XPath 1.0 processors follow whether they are being used in XSLT or not. So expressions that return node-sets are likely to return the nodes in document order, which is the effect you are observing.

XPath 2.0 introduces sequences, which allows you to return nodes in any order of your own choosing.

Concatenate two Node Set with XPath

2 Answers2