如何使用LINQ-to-XML选择特定节点

XElement root = XElement.Parse("<Root><Child1>value1</Child1<Child2>value2</Child2></Root>");
IEnumerable<XElement> childElements = from el in root.Elements()
                                     where el.Name == "Child1"
                                     select el;

XElement root = XElement.Parse("<Root><Child1>value1</Child1<Child2>value2</Child2></Root>");
IEnumerable<XElement> childElements = root.Elements("Child1");

XElement root = XElement.Parse("<Root><Child1>value1</Child1<Child2>value2</Child2></Root>");
XElement childElement = root.XPathSelectElement("Child1");

XElement root = XElement.Parse("<Root><Child1 attribute1='value1'>value1</Child1<Child2 attribute2='value2'>value2</Child2></Root>");
IEnumerable<XAttribute> attributes = from attr in root.Attributes()
                                      where attr.Name == "attribute1"
                                      select attr;

XElement root = XElement.Parse("<Root><Child1 attribute1='value1'>value1</Child1<Child2 attribute2='value2'>value2</Child2></Root>");
IEnumerable<XAttribute> attributes = root.Attributes("attribute1");