Detailed introduction to reading and writing xml files in C#

The XmlTextWriter class allows you to write XML into a file. This class contains many methods and properties, and using these properties and methods can make it easier for you to process XML. To use this class, you must first create a new XmlTextWriter object, and then you can add XML fragments to this object. This class contains many methods for adding various types of XML elements to XML files. The following table gives the names and descriptions of these methods:

method
describe

WriteStartDocument
XML statement with written version "1.0"

WriteEndDocument
Close any open element or attribute

Close
Close the flow

WriteDocType
Write a DOCTYPE declaration with a specified name and optional attributes

WriteStartElement
Write out the specified start mark

WriteEndElement
Close an element

WriteFullEndElement
Close an element and always write the full end mark

WriteElementString
Write out elements containing string values

WriteStartAttribute
The starting content of writing attributes

WriteEndAttribute
Close the previous WriteStartAttribute call

WriteRaw
Manually write original marks

WriteString
Writing a string

WriteAttributeString
Extract attributes with specified values

WriteCData
Write out the <![CDATA[...]]> block containing the specified text

WriteComment
Write a comment containing the specified text <!--...-->

WriteWhiteSpace
Write out the given blank

WriteProcessingInstruction
Write out processing instructions with spaces between the name and text, as shown below: <?name text?>

If you are very familiar with XML, then you will definitely understand the above methods well. Below we will give an example, in which we will create a document, add some elements, and then close the document. After adding elements, you can also add child elements, attributes and other content. The following code is an example of this, which creates an XML file with the file name title.

If you compile and execute the above code, you will create this XML file with the following content:

The above code creates an XmlTextWriter object called writer. When this object is created, it is associated to a file named. Next, the program creates a root property called items, and the WriteStartElement method creates the start tag of this property. Next, the program calls the WriteElementString method to create three child elements. From the above code you can also see that this method uses the first parameter (the title in the above program) as the element's label; and uses the second parameter as the element's value. After you add all the elements, you need to close the root element. At this time, you can call the WriteEndElement method to close the recently opened element; in this example, the recently opened element is the root element. When all the data has been written and the root element has been closed, you can pass the information to your XmlTextWriter. This means that at this time you can call the Close method to close it.

The above code is relatively simple. Let's take a look at an example that uses more methods in the XmlTextWriter class and has more complete functions.

After the above code is compiled and run, the file will be obtained, and the content of the file is:

The comments in the above code illustrate how the functionality of this program is implemented. One thing to remember is: when calling a method starts an operation, you need to call the method to end the operation in the appropriate place in the program. For example, if you call StartElement, you must call EndElement to close the element; of course you can also add a child element between these two calls. Whenever you call the EndElement method, it always closes the element that was recently opened with the StartElement method (this is very similar to how the stack works).

Using XmlTextWriter is very easy, but I still recommend that you try these codes and methods yourself. After you try it, you will find that these codes can be easily integrated into your program. You should also remember that XmlTextWriter is just one of many XML classes provided by .NET. Like XmlTextWriter, other XML classes are also very easy to use.

2）
I'm using a very stupid method, but it can help beginners understand the process of accessing XML nodes.

It is known that there is an XML file () as follows:

1. Insert a <book> node into the <bookstore> node:

The result is:

2. Modify node: Change the genre value of the node with the genre attribute value "Li Zanhong" to "update Li Zanhong", and modify the text of the child node <author> of the node to "Yasheng".

The final result is:

3. Delete the genre attribute of the <book genre="fantasy" ISBN="2-3631-4"> node, and delete the <book genre="updateLi Zanhong" ISBN="2-3631-4"> node.

The final result is:

4. Display all data.