C# XML basics summary (retrieve the content of XML files)

Preface:

Recently, a third-party project was connected to the data transmission format of the project is XML. Since I only came into contact with a small amount of data formats that are XML interfaces when I was in the medical industry for many years, I have almost never been exposed to it since then. Therefore, I still feel that there are many blind spots and shortcomings in XML, so I summarized the XML-related knowledge points through some online information.

What is XML?

XML is an extensible markup language.
XML is a markup language that looks a lot like HTML.
XML is designed to transmit data, not display data.
XML tags are not predefined. You need to define the tags yourself.
XML is designed to be self-descriptive.
XML is the recommended standard for W3C.

Pros and cons of XML

Advantages of XML

The grammar is rigorous, the format is unified, and it meets the standards.
Easy to interact remotely with other systems, and data sharing is more convenient.

Disadvantages of XML

The scalability, flexibility and readability are poor.
XML files are huge, the file format is complex, and the transmission accounts for bandwidth.
The server-side and client-side parsing XML takes a lot of resources and time.

Simple XML example

Online xml verification tool:http://tools./code/xmlcodeformat

&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;books&gt;
    &lt;book&gt;
        &lt;author&gt;Time Chaser&lt;/author&gt;
        &lt;title&gt;XMLStudy tutorial&lt;/title&gt;
        &lt;publisher&gt;Time Publishing House&lt;/publisher&gt;
    &lt;/book&gt;
&lt;/books&gt;

5 predefined entity references in XML

Escape characters	symbol	name
&	&	And number
<	<	Less than
>	>	Greater than
'	'	Ellipsis
"	"	quotation marks

Strictly speaking, it is illegal to have only characters "<" and "&" in XML. Ellipsis, quotes, and greater than are legal. At this time, Xml has two solutions to deal with this problem.

CDATA

Escape characters

C# converts special symbols into escape characters

/// &lt;summary&gt;
        /// Convert special symbols to escape characters        /// &lt;/summary&gt;
        /// &lt;param name="xmlStr"&gt;&lt;/param&gt;
        /// &lt;returns&gt;&lt;/returns&gt;
        public string XmlSpecialSymbolConvert(string xmlStr)
        {
            return ("&amp;", "&amp;amp;").Replace("&lt;", "&amp;lt;").Replace("&gt;", "&amp;gt;").Replace("\'", "&amp;apos;").Replace("\"", "&amp;quot;");
        }

C# Create a simple XML file

/// &lt;summary&gt;
        /// Create Xml file        /// &lt;/summary&gt;
        public void CreateXmlFile()
        {
            XmlDocument xmlDoc = new XmlDocument();
            //Create a type declaration node            XmlNode node = ("1.0", "utf-8", "");
            (node);
            //Create Xml root node            XmlNode root = ("books");
            (root);

            XmlNode root1 = ("book");
            (root1);

            //Create child nodes            CreateNode(xmlDoc, root1, "author", "Time Chaser");
            CreateNode(xmlDoc, root1, "title", "XML Learning Tutorial");
            CreateNode(xmlDoc, root1, "publisher", "Time Publishing House");
            //Save the file to the specified location            ("D://");
        }

        /// &lt;summary&gt;    
        /// Create node        /// &lt;/summary&gt;    
        /// <param name="xmlDoc">xml document</param>        /// <param name="parentNode">Xml parent node</param>        /// <param name="name">Node name</param>        /// <param name="value">node value</param>        ///   
        public void CreateNode(XmlDocument xmlDoc, XmlNode parentNode, string name, string value)
        {
            //Create the corresponding Xml node element            XmlNode node = (, name, null);
             = value;
            (node);
        }

Create the generated Xml file

&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;books&gt;
  &lt;book&gt;
    &lt;author&gt;Time Chaser&lt;/author&gt;
    &lt;title&gt;XMLStudy tutorial&lt;/title&gt;
    &lt;publisher&gt;Time Publishing House&lt;/publisher&gt;
  &lt;/book&gt;
&lt;/books&gt;

C# Add nodes in XML file

This time we did operations in the last newly created XML file, adding a new node named publishdate under the book secondary node, and the value of this node is 2022-03-26.

private static void AppendNode()
        {
            XmlDocument xmlDoc = new XmlDocument();
            ("D://");//Load the Xml file            XmlNode root = ("books/book");//Select the book node to add child nodes            //Create a new Xml node element            XmlNode node = (, "publishdate", null);
             = "2022-03-26";
            (node);//Add the created item child node to the tail of the item node            ("D://");//Save the modified Xml file content        }

XML file content after successful addition of node

&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;books&gt;
  &lt;book&gt;
    &lt;author&gt;Time Chaser&lt;/author&gt;
    &lt;title&gt;XMLStudy tutorial&lt;/title&gt;
    &lt;publisher&gt;Time Publishing House&lt;/publisher&gt;
    &lt;publishdate&gt;2022-03-26&lt;/publishdate&gt;
  &lt;/book&gt;
&lt;/books&gt;

C# Modify the data of XML file nodes

This time we operated in the first newly created XML file, and changed the content of author under the second-level node of the book to: Da Yao classmate

private static void UpdateXml()
        {
            XmlDocument xmlDoc = new XmlDocument();
            ("D://");//Load the Xml file            XmlNode xns = ("books/book");//Find the node to be modified            XmlNodeList xmlNodeList = ;//Retrieve all child nodes under the book node
            foreach (XmlNode xmlNode in xmlNodeList)
            {
                XmlElement xmlElement = (XmlElement)xmlNode;//Convert the node to type                if (=="author")//Distinguish whether the child node is the node to be searched                {
                     = "Yao Classmate";//Set new value                    break;
                }
            }
            ("D://");//Save the modified Xml file content        }

Modified XML file content

&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;books&gt;
  &lt;book&gt;
    &lt;author&gt;Classmate Da Yao&lt;/author&gt;
    &lt;title&gt;XMLStudy tutorial&lt;/title&gt;
    &lt;publisher&gt;Time Publishing House&lt;/publisher&gt;
  &lt;/book&gt;
&lt;/books&gt;

C# deletes the specified node in the XML file

This time we operated in the first newly created XML file and deleted the author node.

private static void DeleteXmlNode()
        {
            XmlDocument xmlDoc = new XmlDocument();
            ("D://");//Load the Xml file            XmlNode xns = ("books/book");//Find the root node to be deleted
            #region Delete author node
            var delNode = ("books/book/" + "author");
            (delNode);

            #endregion

            ("D://");//Save the Xml file content after the operation        }

C# clears the specified XML node data

This time we operated in the first newly created XML file to clear the data under the author node.

private static void ClearDataXmlNode()
        {
            XmlDocument xmlDoc = new XmlDocument();
            ("D://");//Load the Xml file            XmlNode xns = ("books/book");//Find the root node to be deleted
            #region Clear data under author node            XmlNodeList xmlNodeList = ;//Retrieve all child nodes under the book node            foreach (XmlNode xmlNode in xmlNodeList)
            {
                XmlElement xmlElement = (XmlElement)xmlNode;//Convert the node to type                if ( == "author")//Distinguish whether the child node is the node to be searched                {
                    //Clear the data under the author node                    ();//Delete all contents of this node                }
            }
            #endregion

            ("D://");//Save the Xml file content after the operation        }

Learning reference materials

w3cSchool-XML Tutorial

Summary of common classes and attributes used to control XML serialization in .NET

This is the article about the introduction to the basic introduction of C# XML (add, delete, modify and clarify the content of XML files). For more related basic introduction of C# XML, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!