merge all XML file in a folder in C#

Question

I want to merge all xml files in a folder. Here i am giving sample two xml files:

My first xml file is like this:

 

<first>
   <second>
      <third>123</third>
         <text>
            <type>text1</type>
            <country>fr</country>
            <vaue>No1</value>
         </text>
      <third>345</third>
           <text>
           <type>text2</type>
           <country>fr</country>
           <vaue>No2</value>
         </text>
   </second>
</first>

 My second xml file is like this:

<first>
   <second>
      <third>123</third>
         <text>
            <type>text1</type>
            <country>in</country>
            <vaue>No5</value>
         </text>
      <third>345</third>
         <text>
            <type>text2</type>
            <country>in</country>
            <vaue>No3</value>
         </text>
      </second>
</first>

The output should be like this:

<first>
     <second>
         <third>123</third>
            <text>
               <type>text1</type>
               <country>fr</country>
               <vaue>No1</value>
            </text>
            <text>
               <type>text1</type>
               <country>in</country>
               <vaue>No5</value>
            </text>
         <third>345</third>
            <text>
               <type>text2</type>
               <country>in</country>
               <vaue>No3</value>
            </text>
            <text>
            <type>text2</type>
            <country>in</country>
            <vaue>No2</value>
         </text>
   </second>
</first>

I have tried it in C# like this, but it is not giving me the correct output:

string[] files = get all files in a directory;

var masterfile = new XDocument();
string readAllText1 = File.ReadAllText(files[0]);
StreamReader sr = new StreamReader(files[0], true);
XDocument xdoc1 = XDocument.Load(sr);

XElement newDocument = new XElement(xdoc1.Root);

masterfile.Add(newDocument);
foreach (var file in files)
{
if (file != files[0])
{
StreamReader sr1 = new StreamReader(file, true);
XDocument xdoc = XDocument.Load(sr1);
masterfile.Root.Add(xdoc.Descendants("third"));
}
}
string str = Path.GetFileNameWithoutExtension(files[0]).Remove(Path.GetFileNameWithoutExtension(files[0]).Length - 3);
masterfile.Save(textBox2.Text + "//" + str + ".xml");

Advance thanks,

Darma