Getting an ajax-generated image from web-form C#

Question

Hello. I'm trying to automatize a process of filling a web form. I want to take values from database, fill the web-form with them and submit the form. Before submitting I should fill a field with numbers written on capcha-image. As far as I can't recognize the capcha by my program, I want to get it from the form, show it to user by win-application.
Could you please tell me how to get the image from web-form and put in into Image class (C#)? Here's an example of html-code:

<form id="work_permit" name="searchform" method="get" action="/prfrequest">



            <ul>
                <li>
                    <span>smth&nbsp;smth</span> 
            <strong  class="info_area" ><input type="text" value=""  maxlength="4" name="series" /></strong>


            </li>
                        <li>
            <span>smth&nbsp;smth</span> 
            <strong  class="info_area"><input type="text" value=""  maxlength="6" name="num" /></strong>

            </li>
                        <li>
            <span>E-mail</span>

            <strong class="info_area"><input  type="text" value="" name="email" /></strong>


            </li>
                        </ul>




                       <div class="instruction">
            <p><strong>smth</strong></p>
            </div>

                        <div class="capctcha_main">
            <div class="cap_form"><img id="xpic" src="../img/official/ajax-loader5.gif" /></div>

I need to get image with id=xpic