read xml file and convert it to byte

[C# Programming]

i have code like this

public void Page_Load(object e, EventArgs s)
{
try
{
XmlDocument doc = new XmlDocument();
byte[] chunk;
string message;
string xmlmessage;
xmlmessage = "" +
"SSdtIGp1c3QgYSBsaXR0bGUgYml0IGNhdWdodCBpbiB0aGUgbWlkZGxlDQpMaWZlIGlzIGEg" +
"bWF6ZSBhbmQgbG92ZSBpcyBhIHJpZGRsZQ0KSSBkb24ndCBrbm93IHdoZXJlIHRvIGdvIEkg" +
"Y2FuJ3QgZG8gaXQgYWxvbmUgSSd2ZSB0cmllZA0KQW5kIEkgZG9uJ3Qga25vdyB3aHkNCg0K" +
"U2xvdyBpdCBkb3duDQpNYWtlIGl0IHN0b3ANCk9yIGVsc2UgbXkgaGVhcnQgaXMgZ29pbmcg" +
"dG8gcG9wDQonQ2F1c2UgaXQncyB0b28gbXVjaA0KWWVhaCwgaXQncyBhIGxvdA0KVG8gYmUg" +
"c29tZXRoaW5nIEknbSBub3QNCg0KSSdtIGEgZm9vbA0KT3V0IG9mIGxvdmUNCidDYXVzZSBJ" +
"IGp1c3QgY2FuJ3QgZ2V0IGVub3VnaA0KDQpJJ20ganVzdCBhIGxpdHRsZSBiaXQ=";
doc.LoadXml(xmlmessage);
XmlNode node = doc.SelectSingleNode("chunk");
chunk = node.Value ;// thi is my error, i wanto to read the value as byte
Response.Write("sucsess ");
}
catch (Exception x)
{
Response.Write("error "+x);
}

}

can some body help me solve my problem or give me suggestion to solve the problem, thx

regards
novhard