Simply parse XmlElement.InnerText property to specific type :
bool mybool = Boolean.Parse(myXmlElement.InnerText);
UPDATE :
you can use Convert.ChangeType() method to parse string from Xml to given Type
variable :
Type myType;
if(myType == typeof(Boolean) || myType == typeof(Double))
{
object myvalue = Convert.ChangeType(xmlElement.InnerText, myType);
}