title: ConfigurationSettings.AppSettings is obsolete
body: <p>The following code works fine:</p>
  
  <pre><code>string api_url = ConfigurationSettings.AppSettings["api-url"].ToString();
  </code></pre>
  
  <p>with a warning message as follows:</p>
  
  <blockquote>
    <p>'System.Configuration.ConfigurationSettings.AppSettings' is obsolete: '"This method is obsolete, it has been replaced by System.Configuration!System.Configuration.ConfigurationManager.AppSettings"'</p>
  </blockquote>
  
  <p>As suggested by the warning message, I tried replacing <code>ConfigurationSettings.AppSettings</code> with <code>ConfigurationManager.AppSettings</code></p>
  
  <pre><code>string api_url = ConfigurationManager.AppSettings["api-url"].ToString();
  </code></pre>
  
  <p>Now an error message appears, stating:</p>
  
  <blockquote>
    <p>The name 'ConfigurationManager' does not exist in the current context</p>
  </blockquote>
  
  <p>These are the namespaces imported:</p>
  
  <pre><code>using System;
  using System.Collections.Generic;
  using System.ComponentModel;
  using System.Data;
  using System.Drawing;
  using System.Linq;
  using System.Text;
  using System.Windows.Forms;
  using System.Configuration;
  </code></pre>
  
  <p>Please help me.</p>