Linq to Xml 增删查改

LINQ to XML一个重要的特性是能够方便地修改xml树，如添加、删除、更新和复制xml文档的内容。

I.插入

使用XNode类的插入方法可以方便地向xml树添加内容：

在下面的示例中，使用AddAfterSelf方法向现有xml中添加一个新节点：

	public static void AddAfterSelf()
        {
            XElement root = XElement.Parse(@"

                <Categories>

                  <Category>

                    <CategoryID>1</CategoryID>

                    <CategoryName>Beverages</CategoryName>

                    <Description>Soft drinks,coffees,teas,beers,and ales</Description>

                  </Category>

                </Categories>

            ");
            XElement xele = root.Element("Category").Element("CategoryName");
            xele.AddAfterSelf(new XElement("AddDate",DateTime.Now));
            //保存
            root.Save("test.xml");
        }

<?xml version="1.0" encoding="utf-8"?>
<Categories>
  <Category>
    <CategoryID>1</CategoryID>
    <CategoryName>Beverages</CategoryName>
    <AddDate>2013-07-22T21:51:42.1550551+08:00</AddDate>
    <Description>Soft drinks,and ales</Description>
  </Category>
</Categories>

II.更新

在LINQ to XML中更新xml内容可以使用以下几种方法：

在下面的示例中使用了ReplaceWith与SetElementValue方法对xml进行了更新操作：

	public static void Update()
        {
            XElement root = XElement.Parse(@"
                                   <Categories>
                                      <Category>
                                        <CategoryID>1</CategoryID>
                                        <CategoryName>Beverages</CategoryName>
                                        <Description>Soft drinks,and ales</Description>
                                      </Category>
                                    </Categories>
                                  ");
            root.Element("Category").Element("CategoryID").ReplaceWith(new XElement("ID","2"));
            root.Element("Category").SetElementValue("CategoryName","test data");
            root.Save("test.xml");
        }

<?xml version="1.0" encoding="utf-8"?>
<Categories>
  <Category>
    <ID>2</ID>
    <CategoryName>test data</CategoryName>
    <Description>Soft drinks,and ales</Description>
  </Category>
</Categories>

III.删除

可以使用Remove(XElement)与RemoveAll方法来删除xml。

在下面的示例中，使用了RemoveAll方法：

	public static void Remove()
        {
            string path = @"test.xml";
            XElement root = XElement.Parse(@"
                                  <Categories>

                                    <Category>

                                      <CategoryID>1</CategoryID>

                                      <CategoryName>Beverages</CategoryName>

                                      <Description>Soft drinks,and ales</Description>

                                    </Category>

                                  </Categories>

                                ");
            root.RemoveAll();
            root.Save(path);
        }

<?xml version="1.0" encoding="utf-8"?>
<Categories />

	public static void Remove()
        {
            XElement root = XElement.Parse(@"
                                <Categories>
                                  <Category>
                                    <CategoryID>1</CategoryID>
                                    <CategoryName>Beverages</CategoryName>
                                    <Description>Soft drinks,and ales</Description>
                                  </Category>
                                </Categories>
                                ");
            root.Element("Category").Element("Description").Remove();
            root.Save("test.xml");
        }

<?xml version="1.0" encoding="utf-8"?>
<Categories>
  <Category>
    <CategoryID>1</CategoryID>
    <CategoryName>Beverages</CategoryName>
  </Category>
</Categories>

	public static void AddAttribute()
        {
            XElement root = new XElement("Categories",new XElement("Category",new XAttribute("CategoryID","1"),new XElement("CategoryName","Beverages"),new XElement("Description","Soft drinks,and ales")
                )
            );
            root.Element("Category").Add(new XAttribute("AddDate",DateTime.Now.ToShortDateString()));
            root.Save("test.xml");
        }

<?xml version="1.0" encoding="utf-8"?>
<Categories>
  <Category CategoryID="1" AddDate="2013/7/22">
    <CategoryName>Beverages</CategoryName>
    <Description>Soft drinks,and ales</Description>
  </Category>
</Categories>

	public static void SelectAttribute()
        {
            XElement root = new XElement("Categories",and ales")
                )
            );
            XAttribute xattr = root.Element("Category").Attribute("CategoryID");
            Console.WriteLine(xattr.Name);
            Console.WriteLine(xattr.Value);
        }