问如何从XPathNodeIterator获取元素值？

EN

XPathNodeIterator it;

string selectStr = "Equipment/Group/item";
it = nav.Select(selectStr);
while (it.MoveNext())
{
    String strVal = "";
    if (it.Current.HasChildren)
    {
        strVal = it.Current.Value.ToString(); // get wrong value here. I want to get 'COM' and 'MD'
    }
}

<Equipment xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <License licenseId="" licensePath=""/>
  <Group>
    <item>
      <key>COM</key>
      <value>
        <format>10</format>
        <value>0</value>
      </value>
    </item>
    <item>
      <key>MD</key>
      <value>
        <format>20</format>
        <value>test</value>
      </value>
    </item>
.....