title: Textbox not displaying value after selecting from ComboBox Dropdown
body: <p>so I have a <code>Combo Box</code> and I have a list made using a <code>KeyValuePair&lt;int, decimal&gt;</code>. I want the textbox I have selected to show the value according to the key when I select it from drop-down textbox.</p>
  
  <p>Relevant code:</p>
  
  <pre><code>// Make a list of truck weight and MPG.
  List&lt;KeyValuePair&lt;int, decimal&gt;&gt; weightMPG = new List&lt;KeyValuePair&lt;int, decimal&gt;&gt;();
  
  private void mainForm_Load(object sender, EventArgs e)
  {
      decimal k = 7;
      for (int i = 20000; i &lt; 40000; i+=1000){
          weightMPG.Add(new KeyValuePair&lt;int, decimal&gt;(i, k));
          k -= 0.1m;
      }
      for (int i = 40000; i &lt; 45000; i+=1000){
          weightMPG.Add(new KeyValuePair&lt;int, decimal&gt;(i, 5));
      }
      weightMPG.Add(new KeyValuePair&lt;int, decimal&gt;(46000, 4.9m));
      weightMPG.Add(new KeyValuePair&lt;int, decimal&gt;(47000, 4.8m));
      weightMPG.Add(new KeyValuePair&lt;int, decimal&gt;(48000, 4.7m));
      truckWeight2.DataSource = weightMPG;
      truckWeight2.ValueMember = "Value";
      truckWeight2.DisplayMember = "Key";
  }
  
  private void truckWeight2_SelectedIndexChanged(object sender, EventArgs e)
  {
      truckMPG2.Text = truckWeight2.ValueMember;
  }
  </code></pre>
  
  <p>For this code, it shows a dropdown from 20,000 to 48,000 when I click the control. However when I select one, the textbox (<code>truckMPG2</code>) doesn't update to reflect the value, rather it just always displays word "Value."</p>
  
  <p>I've looked at other stack-overflow answers when making this code, so I'm not sure where I am going wrong.</p>