LINQ to read XML

I got this XML file:

<root>
    <level1 name="A">
        <level2 name="A1" />
        <level2 name="A2" />
    </level1>
    <level1 name="B">
        <level2 name="B1" />
        <level2 name="B2" />
    </level1>
    <level1 name="C" />
</root>

Could someone give me a C# code using LINQ, the simplest way to print this result:
(Note the extra space if it is a level2 node)

A
  A1
  A2
B
  B1
  B2
C

Currently I got this code:

XDocument xdoc = XDocument.Load("data.xml"));
var lv1s = from lv1 in xdoc.Descendants("level1")
           select lv1.Attribute("name").Value;

foreach (var lv1 in lv1s)
{
    result.AppendLine(lv1);

    var lv2s = from lv2 in xdoc...???
}