This is a simple PHP function (that can easily be replicated in .NET) that will take a string and get the first paragraph of text it can find. Works with HTML and plain text.

We use it on the UMN Homecoming site for the "Latest Blog Post."

In PHP:

/**
 * Simple function gets first paragraph of text, supports HTML or plain text.
 *
 * @author Kamran Ayub
 * @param {String} $data The string to summarize
 * @param {Boolean} $isHTML Whether or not the string contains HTML
 */
function string_summarize($data, $isHTML = true) {    
    
    $result = $data;
    
    if($isHTML) {
        
        // convert line breaks/paragraphs
        $result = str_replace("
", "", $result); // remove extra
        $result = str_replace("<br>", "
", $result);
        $result = str_replace("<br/>", "
", $result);
        $result = str_replace("<br />", "
", $result);
        $result = str_replace("</p>", "

", $result);
    
        // strip all remaining tags
        $result = strip_tags($result);
    }
    
    // try and return the first paragraph, if I can't, return all of it
    $paragraphs = explode("

", trim($result));
    
    if(count($paragraphs) > 1) {
        return nl2br(trim($paragraphs[0]));
    } else {
        return $data;
    }
}

Enjoy!