foreach (XmlNode node in baseNode.ChildNodes)
{
string innerXml = node.innerXml;
switch (node.Name)
{
case "created_at":
time = innerXml;
break;

case "text":
text = innerXml;
break;

case "source":
source = innerXml;
break;
....

ってXML解析やるの面倒で冗長なんだけど
source = node["source"]みたいにならないですか