title: Connection strings is not working
body: <p>I am developing windows application in C# and i used sql server 2008 database.I have declared my connection string in <code>app.config</code> like this:</p>
  
  <pre><code>&lt;connectionStrings&gt;
        &lt;add name="constr" connectionString="server=lexecute-pc;database=lexecute_window;integrated security=true"/&gt;
        &lt;/connectionStrings&gt;
  </code></pre>
  
  <p>And in my .cs page i am calling connection string like this:</p>
  
  <pre><code>    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["constr"].ToString());
  </code></pre>
  
  <p>But when I run this page I got following exception:</p>
  
  <blockquote>
    <p>Configuration system failed to initialize</p>
  </blockquote>
  
  <p>Please help me.</p>