XML and Visual c# problem

private void button1_Click(object sender, EventArgs e)
{
System.IO.StreamReader sr = new System.IO.StreamReader(@"people.xml");
System.Xml.XmlTextReader xr = new System.Xml.XmlTextReader(sr);
System.Xml.XmlDocument peopledoc = new System.Xml.XmlDocument();

//load up the xml file
peopledoc.Load(xr);
System.Xml.XmlNodeList peopleitems = peopledoc.SelectNodes("people/person");
System.Xml.XmlNode people1 = peopleitems.Item(0).SelectSingleNode("firstname");
System.Xml.XmlNode people2 = peopleitems.Item(0).SelectSingleNode("lastname");
System.Xml.XmlNode people3 = peopleitems.Item(0).SelectSingleNode("age");

listBox1.Items.Add(people1.InnerText + " " + people2.InnerText);
listBox1.Items.Add("Age: " + people3.InnerText);

System.Xml.XmlNode people4 = peopleitems.Item(1).SelectSingleNode("firstname");
System.Xml.XmlNode people5 = peopleitems.Item(1).SelectSingleNode("lastname");
System.Xml.XmlNode people6=peopleitems.Item(1).SelectSingleNode("age");

add_space();

listBox1.Items.Add(people4.InnerText+" "+people5.InnerText);
listBox1.Items.Add("Age: "+people6.InnerText);

//This is where I get the exception
System.Xml.XmlNode people7 = peopleitems.Item(2).SelectSingleNode("firstname");
System.Xml.XmlNode people8 = peopleitems.Item(2).SelectSingleNode("lastname");
System.Xml.XmlNode people9 = peopleitems.Item(2).SelectSingleNode("age");

add_space();

listBox1.Items.Add(people7.InnerText + " " + people8.InnerText);
listBox1.Items.Add("Age: " + " " + people9.InnerText);

and the following XML file:

Why do I get a Null reference exception when trying to read the third entry (creating the people 7,8,9 variables)?

Also is there a way of using a foreach loop to make the code a lot smaller ? ;)

[9609 byte] By [MartinHooper] at [2008-2-7]