<root>
<child id = 1> <subroot> <element id = 1 /> </subroot> </child>
<child id = 2 > <subroot> <element id = 2 /> </subroot> </child>
<child id = 3> <subroot> <element id = 3 /> </subroot> </child>
<child id =4 > <subroot> <element id = 4 /> </subroot> </child>
<child id = 5> <subroot> <element id = 5 /> </subroot> </child>
<child id =6> <subroot> <element id = 6 /> </subroot> </child>
</root>
In the above xml, I need to get the "child" nodes and again needs to query the subroot nodes using xpath.
xpath to get child node :
XmlNodelist child = doc.SelectNodes("//root/ch
foreach(XmlNode item in XmlNodeList)
{
item.selectnodes(//subroot
}
but the second xpath query, again searches from root node. how set the child node as root?
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Hi,
I've seen this problem before when using c#, I resolved it by using placing a dot or . in front of the '//' in order to ensure that I am in the current context. So you should use this:
foreach(XmlNode item in XmlNodeList)
{
item.selectnodes(".//subro
}
using this method allows you to select the current element without knowing it name. Let me know how this works out.
Enjoy!
P.
wel, that is true of course,
It has nothing to do with C#, it is simple XPath
1. "//subroot" finds all the subroot from the start of the document at any depth
2. ".//subroot" finds all the subroot from the current context at any depth
3. "subroot" finds all the child elements subroot
1. is wrong because you don't want to start from the top of the document
2. is correct, but not so good if you need child elements, because it starts looking for subroot nodes at any depth, and this is highly inefficient unless you don't know were the subroot elements are (at what depth)
3. is optimal for this XML, since it goes straight to the child elements. Highest performance
summary: the dot is not incidentally for C#, it is common XPath, but pui_yun's suggestion is only a good one if you don't know where the subroot elements are. Avoid using "//" or ".//" in XPath if you don't really need them
When talking about xpath, any xpath starting with '/' tells us that we are selecting from the root, however, it's easy to make the mistake esp when we are selecting from an XmlNode to assume that the node is the "root" and not just the context.
The '//' is equivalent to "/descendant::' which if that is what you are trying to do (i.e. selecting all descendant of that node with an element name subroot), then well you can do it that way, however, you as gertone mention, this can lead to less than optimal code (and maybe incorrect code), esp if this isn't what you are trying to do esp. if you have nested subroot elements (unless you want to select the nested elements as well).
Hope this helps.
P.
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by: GertonePosted on 2009-11-07 at 23:34:10ID: 25769697
your Xpath should not start with "//"
Try ("subroot")