How to Read xml data when i pass specific id?

Question

i have requirement that i have to read xml data for specific id. for example i want to

retrieve all district names in id:21. can any one please help me

<?xml version="1.0" encoding="utf-8" ?>

<Rnames>

<org id="19">

<District name="District 19A1"/>

<District name="District 19A2"/>

<District name="District 19A3"/>

<District name="District 19A4"/>

</org>

<org id="20">

<District name="District 20A1"/>

<District name="District 20A2"/>

</org>

<org id="21">

<District name="District 21A1"/>

<District name="District 21A2"/>

<District name="District 21A3"/>

<District name="District 21A4"/>

</org>

<org id="22">

<District name="District 22A1"/>

<District name="District 22A2"/>

</org>

<org id="23">

<District name="District 23A1"/>

<District name="District 23A2"/>

</org>

</Rnames>