Compare two XML file

Question

Hi,

I have two XML file. One is given by the user say Source.xml and other is given by the application it self means load from the main project.

Like,

Source.xml : 

<input>
  <data>001</data>
  <data>002</data>
  <data>005</data>
</input>

Mapping.xml :

<map>
  <default>?-?-?</default>
    <input value="001">RZ</input>
    <input value="002">TH</input>
    <input value="003">SC</input>
</map>

And resultant output I want is : 

<output>
  <data>RZ</data>
  <data>TH</data>
  <data>?-?-?</data>
</output>

It means I just want to map two xml file and want the output as shown above.
So, please help me to do so. I am new to asp.net.