Adding XElement to XML file using Linq to XML

Question

Using Linq to XML, I am trying to add an XElement to an existing XML file. It has to be done in the Windows Phone .NET framework. Currently my XML file looks like this:

    <?xml version="1.0" encoding="utf-8"?>
    <Kids>
      <Child>
        <Name>Kid1</Name>
        <FirstName>hisname</FirstName>
      </Child>
    </Kids>

and my code looks like this:



    using (IsolatedStorageFileStream stream = 
               new IsolatedStorageFileStream("YourKids.xml", fileMode, store))
    { 
        XDocument x = XDocument.Load(stream);
        XElement t =  new XElement("Child",
                                           new XElement("Name", pName),
                                           new XElement("FirstName", pFirstname));

       t.Add(from el in x.Elements()
             where el == el.Descendants("Child").Last()
             select el);

       x.Save(stream);
    }

this doesn't do what I want to achieve. I want to add a new "Child" element to the the exisiting XML file like this :

     <?xml version="1.0" encoding="utf-8"?>
    <Kids>
      <Child>
        <Name>Kid1</Name>
        <FirstName>hisname</FirstName>
      </Child>
    <Child>
        <Name>kid2</Name>
        <FirstName>SomeName</FirstName>
      </Child>
    </Kids>

Could use some help because I am stuck ;-)

After the tips from GSerjo, my code looks like this now:

 try
            {

                if (store.FileExists("YourKids.xml"))
                {



                    using (IsolatedStorageFileStream stream = new IsolatedStorageFileStream("YourKids.xml",FileMode.Open, store))
                    {


                        var x = XElement.Load(stream);
                        var t =  new XElement("Child",
                                                        new XElement("Name", pName),
                                                        new XElement("FirstName", pFirstname)
                                                                  );

                        x.Add(t);

                        x.Save(stream);




                        stream.Close();
                        return;
                    }

                }
                else
                {



                    using (IsolatedStorageFileStream CreateIsf = new IsolatedStorageFileStream("YourKids.xml",FileMode.Create,store))
                    {

                        var xDoc = new XElement("Kids",
                                                     new XElement("Child",
                                                       new XElement("Name", pName),
                                                       new XElement("FirstName", pFirstname)
                                                                 )

                                                  );

                        xDoc.Save(CreateIsf);
                        CreateIsf.Close();

                        return;
                    }
                }
            }
            catch (Exception ex)
            {
              message = ex.Message;
            }

Which gives me an xml file like this:

<?xml version="1.0" encoding="utf-8"?>
<Kids>
  <Child>
    <Name>test</Name>
    <FirstName>test</FirstName>
  </Child>
</Kids><?xml version="1.0" encoding="utf-8"?>
<Kids>
  <Child>
    <Name>test</Name>
    <FirstName>test</FirstName>
  </Child>
  <Child>
    <Name>testing</Name>
    <FirstName>testing</FirstName>
  </Child>
</Kids>

Which is still not correct, any ideas anyone ?

GSerjo · Accepted Answer · 2012-08-14T19:57:02.910

Initial xml file

<?xml version="1.0" encoding="utf-8"?>
<Kids>
  <Child>
    <Name>Kid1</Name>
    <FirstName>hisname</FirstName>
  </Child>
</Kids>

Following code add one new child to existing xml

    [Test]
    public void Test()
    {
        string filPath = @"YourKids.xml";
        var root = XElement.Load(filPath);
         var newChild =  new XElement("Child",
                                   new XElement("Name", "NewName"),
                                   new XElement("FirstName", "NewFirstName"));
         root.Add(newChild);
        root.Save(filPath);
    }

Result xml file

<?xml version="1.0" encoding="utf-8"?>
<Kids>
  <Child>
    <Name>Kid1</Name>
    <FirstName>hisname</FirstName>
  </Child>
  <Child>
    <Name>NewName</Name>
    <FirstName>NewFirstName</FirstName>
  </Child>
</Kids>

Update

Bug on save, you should set stream length to 0

Explanation

After reader existing file, stream does not remove any data

using (IsolatedStorageFileStream stream = new IsolatedStorageFileStream("YourKids.xml",FileMode.Open, store))
                    {
                        var x = XElement.Load(stream);

So when you call, data has been appended

   x.Save(stream);
   stream.Close();

Add stream.SetLength(0); before x.Save(stream); and all data will be overwritten.

Here is full version

            if (store.FileExists("YourKids.xml"))
            {
                using (var stream = new IsolatedStorageFileStream("YourKids.xml", FileMode.Open,
                                                                                     store))
                {
                    var x = XElement.Load(stream);
                    var t = new XElement("Child",
                                         new XElement("Name", pName),
                                         new XElement("FirstName", pFirstname)
                        );
                    x.Add(t);
                    stream.SetLength(0);
                    x.Save(stream);
                    stream.Close();
                }
            }
            else
            {
                using (var CreateIsf = new IsolatedStorageFileStream("YourKids.xml", FileMode.Create, store))
                {
                    var xDoc = new XElement("Kids",
                                            new XElement("Child",
                                                         new XElement("Name", pName),
                                                         new XElement("FirstName", pFirstname)
                                                )
                        );
                    xDoc.Save(CreateIsf);
                    CreateIsf.Close();
                }
            }

Please note: I've removed return statements as useless.

P.S. Take a look on resharper, it can improve code.

Wow, thx for te quick reply. Althoug it adds the new child element to my XML file, but strangly enough it keeps my initial xml file and adds the result xml file under my iniital file, making the xml file look like: Kid1 hisname Kid1 hisname NewName NewFirstName — user717316, Aug 14 '12 at 07:10
Looks like you incorrect save result, root.Save(filPath) - replace existing file. Could you please show your last code — GSerjo, Aug 14 '12 at 08:33
I have edited my first post with the full code so you can see how I am saving my xml file. — user717316, Aug 14 '12 at 17:57

Adding XElement to XML file using Linq to XML

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