Update XML with C# using Linq

Question

MY XML FILE STRUCTURE

<items>
  <item>
    <itemID>1</itemID>
    <isGadget>True</isGadget>
    <name>Star Wars Figures</name>
    <text1>LukeSkywalker</text1>
  </item>
</items>

TO READ DATA FROM XML BY ITEMID

XDocument xmlDoc = XDocument.Load(HttpContext.Current.Server.MapPath("data.xml"));
var items = from item in xmlDoc.Descendants("item")
            where item.Element("itemID").Value == itemID
            select new
            {
                itemID = item.Element("itemID").Value,
                isGadget = bool.Parse(item.Element("isGadget").Value),
                name = item.Element("name").Value,
                text1 = item.Element("text1").Value,
             }

foreach (var item in items)
{
     ....
}

How to update XML data by itemID? Thanks!

I dont understand why theses LINQ-to-XML questions are so pervasive at the moment. The answers are right here. msdn.microsoft.com/en-us/library/bb387087.aspx — Gusdor
– Gusdor, Commented Oct 3, 2013 at 7:45

Canavar · Accepted Answer · 2009-09-29 20:22:17Z

19

To update your xml use SetElementValue method of the XElement :

var items = from item in xmlDoc.Descendants("item")
    where item.Element("itemID").Value == itemID
    select item;

foreach (XElement itemElement in items)
{
    itemElement.SetElementValue("name", "Lord of the Rings Figures");
}

EDIT : Yes, I tried your example and it saves updated data to the file. Save your updated xml with Save method of the XDocument, here is the code that I tried :

string xml = @"<items>
           <item>
            <itemID>1</itemID>
            <isGadget>True</isGadget>
            <name>Star Wars Figures</name>
            <text1>LukeSkywalker</text1>
           </item>
        </items>";

XDocument xmlDoc = XDocument.Parse(xml);

var items = from item in xmlDoc.Descendants("item")
            where item.Element("itemID").Value == "1"
            select item;

foreach (XElement itemElement in items)
{
    itemElement.SetElementValue("name", "Lord of the Rings Figures");
}

xmlDoc.Save("data.xml");

edited Sep 29, 2009 at 20:22

answered Sep 28, 2009 at 15:39

Canavar

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2 Comments

user180485 Over a year ago

Not working. Maybe I'm missing something. Do I have to add xmlDoc.Save("data.xml")? Even with xmlDoc.Save, it still does not update.

user180485 Over a year ago

Canavar, I was hoping to update the xml file directly instead of having to convert it into a string first. thanks!

Rajamohan Anguchamy · Accepted Answer · 2013-10-03 07:41:33Z

To update your xml use element method method of the XElement :

XDocument xmlDoc = XDocument.Load(HttpContext.Current.Server.MapPath("data.xml"));
var items = (from item in xmlDoc.Descendants("item")
            where item.Element("itemID").Value == itemID
            select item).ToList();
         foreach (var item in items)
         {
                item.Element("itemID").Value=NewValue;
                bool.Parse(item.Element("isGadget").Value)=Newvalue;
                item.Element("name").Value=Newvalue;
                item.Element("text1").Value=Newvalue;
         }
xmlDoc.Save(HttpContext.Current.Server.MapPath("data.xml"));

or

XDocument xmlDoc = XDocument.Load(HttpContext.Current.Server.MapPath("data.xml"));
             foreach (var item in (from item in xmlDoc.Descendants("item")
                where item.Element("itemID").Value == itemID
                select item).ToList())
             {
                    item.Element("itemID").Value=NewValue;
                    bool.Parse(item.Element("isGadget").Value)=Newvalue;
                    item.Element("name").Value=Newvalue;
                    item.Element("text1").Value=Newvalue;
             }
    xmlDoc.Save(HttpContext.Current.Server.MapPath("data.xml"));

you get information form dynamic and update those changes in button click event means, first you checks the Page load following code is present

if(!Page.IsPostBack) { .... }

Jon Skeet · Accepted Answer · 2009-09-28 15:23:41Z

5

Your query is projecting to an anonymous type. If you want to just modify the elements themselves, you want something like:

var items = from item in xmlDoc.Descendants("item")
            where item.Element("itemID").Value == itemID
            select item;

Otherwise known as:

var items = xmlDoc.Descendants("item")
                  .Where(item => item.Element("itemID").Value == itemID);

I suggest you call ToList() as well, so that the whole query is performed and the results stored in a list before you start modifying things:

var items = xmlDoc.Descendants("item")
                  .Where(item => item.Element("itemID").Value == itemID)
                  .ToList();

answered Sep 28, 2009 at 15:23

Jon Skeet

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4 Comments

user180485 Over a year ago

Can you provide a simple example of call toList() to update xml? Do I need to use the foreach loop to setElementValue?

Jon Skeet Over a year ago

Calling ToList() doesn't update the XML, and yes, you'd need to use foreach. You haven't said how you want to update the XML though, so it's somewhat tricky to give an example.

user180485 Over a year ago

Not sure what are the options for updating a XML document. Maybe you can suggest the most efficient method. :)

Gusdor Over a year ago

Can we really recommend calls to ToList? I've seen junior developers get it into their heads that you need a ToList or ToArray after every single query regardless of usage. It seems to me there should be better usage guidelines. This is after all, the gateway to using List<T>.ForEach(). Grim!

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