Insert new XML node using LINQ

Question

XML: 1 aaa 2 bbb

Code

var doc = XDocument.Load (Server.MapPath(".") + "\\Questions.config");
var elements = from element in doc.Descendants("Question")
               select new
               {
                   Id = element.Element("Id").Value,
                   Text = element.Element("Text").Value,
                   Reserver = element.Element("Reserver") != null
               };

StringBuilder builder = new StringBuilder();
foreach (var question in elements)
{
    builder.AppendLine(question.Id + "-" + question.Text);
}
myTextBox.Text = builder.ToString();

how insert new Node 'Question' to XML File

accept the answer if it helped you. you'll get reputation too — Stefan
– Stefan, Commented Mar 13, 2011 at 14:08
What do you want to update the value to, in the XML? You've given sample input - what do you want the output to be? — Jon Skeet
– Jon Skeet, Commented Mar 13, 2011 at 14:13
@beginner: From your text box? Currently you're only updating the value of your text box, not the XML at all. Could I suggest you read my guide to asking SO questions effectively? tinyurl.com/so-hints — Jon Skeet
– Jon Skeet, Commented Mar 13, 2011 at 14:24

Jon Skeet · Accepted Answer · 2011-03-13 14:21:49Z

1

It's unclear exactly what your question means, but the basic process of updating the XML file would be along the lines of:

Load the XML document into memory, as you're already doing
Identify the element you want to change, which will depend on what the criteria are
Update it (e.g. setting the Value property to "kkk" as per your comments)
Save the XML document using doc.Save("file.xml") or something similar

It's hard to be more precise than that without having more precise requirements. As an example though, if you wanted to prefix every Text node in the document with "Question x: " where x is the ID of the question, you might write something like:

var doc = XDocument.Load("file.xml");
var elements = doc.Descendants("Question");

foreach (var question in elements)
{
    int id = (int) question.Element("ID");
    XElement textElement = question.Element("Text");
    textElement.Value = "Question: " + id + " = " + textElement.Value;
}

doc.Save("changed.xml");

Or to change every "aaa" Text element to "kkk":

var doc = XDocument.Load("file.xml");
var elements = doc.Descendants("Text")
                  .Where(x => x.Value == "aaa");

foreach (var textElement in elements)
{
    textElement.Value = "kkk";
}

doc.Save("changed.xml");

answered Mar 13, 2011 at 14:21

Jon Skeet

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1 Comment

beginner Over a year ago

what is doc.Save("changed.xml"); <"changed.xml">

as-cii · Accepted Answer · 2011-03-13 14:17:51Z

1

Are you trying to do something like this?

var doc = XDocument.Load (Server.MapPath(".") + "\\Questions.config");
var elements = from element in doc.Descendants("Question")
               select new
               {
                   Id = element.Element("Id").Value,
                   Text = element.Element("Text").Value,
                   Reserver = element.Element("Reserver") != null
               };

StringBuilder builder = new StringBuilder();
foreach (var question in elements)
{
    builder.AppendLine(question.Id + "-" + question.Text);
}
myTextBox.Text = builder.ToString();

EDIT: If you want to update every question then you have to slightly modify the code above.

var elements = from element in doc.Descendants("Question")
               select new
               {
                   Id = element.Element("Id"),
                   Text = element.Element("Text"),
                   Reserver = element.Element("Reserver")
               };
StringBuilder builder = new StringBuilder();
foreach (var question in elements)
{
    // Read
    builder.AppendLine(question.Id.Value + "-" + question.Text.Value);

    // Write
    question.Reserver.Value = "True";
}
myTextBox.Text = builder.ToString();

In this way you don't select the value anymore but the XElement instead, so you're able to modify the XML. Remember also to save the file using XDocument.Save().

edited Mar 13, 2011 at 14:17

answered Mar 13, 2011 at 14:03

as-cii

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8 Comments

beginner Over a year ago

tanks . very very very muck . how can updata xml by linq

Jon Skeet Over a year ago

It's unclear to me why this answer has been accepted, given that it doesn't modify the XML at all...

as-cii Over a year ago

Hi Jon, the question was different previously. Take a look at the edits ;) Anyway I have updated it with the new requests.

Jon Skeet Over a year ago

@AS-CII: Yes, I hadn't seen the edits - but your answer still doesn't appear to be modifying the XML.

beginner Over a year ago

question.Reserver.Value = "True"; this not work that update Reserver=true

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