Recebo resposta da Web e uso o streamreader para obter a resposta como uma string

my code is

HttpWebResponse response = (HttpWebResponse) request.GetResponse();
StreamReader reader = new StreamReader(response.GetResponseStream());
string strResponse = reader.ReadToEnd();

semple de string é

<div class="box-round">
<ol  style="list-style-type: decimal;list-style-position:outside;margin-left:42px;">
<li>Order ID #A123456 already exists: Update performed
</ol>
</div>

o

<div class="box-round">
    <ol  style="list-style-type: decimal;list-style-position:outside;margin-left:42px;">
    <li>New order created
    </ol>
</div>

Quero localizar a seguinte linha dentro da string

Order ID #A123456 already exists: Update performed

o

New order created

Esta é a melhor maneira de procurar as linhas

  while (!reader.EndOfStream)
    {
        line = reader.ReadLine();
        if (!string.IsNullOrEmpty(line))
        {

        }
    }