Modify XML existing content in C#

Question

Purpose: I plan to Create a XML file with XmlTextWriter and Modify/Update some Existing Content with XmlNode SelectSingleNode(), node.ChildNode[?].InnerText = someting, etc.

After I created the XML file with XmlTextWriter as below.

XmlTextWriter textWriter = new XmlTextWriter("D:\\learning\\cs\\myTest.xml", System.Text.Encoding.UTF8);

I practiced the code below. But failed to save my XML file.

XmlDocument doc = new XmlDocument();
doc.Load("D:\\learning\\cs\\myTest.xml");

XmlNode root = doc.DocumentElement;
XmlNode myNode;

myNode= root.SelectSingleNode("descendant::books");

....

textWriter.Close();

doc.Save("D:\\learning\\cs\\myTest.xml");  

I found it is not good to produce like my way. Is there any suggestion about it? I am not clear about the concepts and usage of both XmlTextWriter and XmlNode in the same project. Thank you for reading and replies.

Unclog

What node are you trying to retrieve? Could you post some of the xml you are using? I am not aware of descendant::books xpath syntax. Also you don't need the XmlTextWriter, just the XmlDocument – Araliaceous

Answer 1

Well, If you want to update a node in XML, the XmlDocument is fine - you needn't use XmlTextWriter.

XmlDocument doc = new XmlDocument();
doc.Load("D:\\build.xml");
XmlNode root = doc.DocumentElement;
XmlNode myNode = root.SelectSingleNode("descendant::books");
myNode.Value = "blabla";
doc.Save("D:\\build.xml");

Qoph

Answer 2

Using LINQ to xml if you are using framework 3.5

using System.Xml.Linq;

XDocument xmlFile = XDocument.Load("books.xml"); 
var query = from c in xmlFile.Elements("catalog").Elements("book")    
            select c; 
foreach (XElement book in query) 
{
    book.Attribute("attr1").Value = "MyNewValue";
}
xmlFile.Save("books.xml");

Carlsbad

Answer 3

Forming a XML file

XmlTextWriter xmlw = new XmlTextWriter(@"C:\WINDOWS\Temp\exm.xml",System.Text.Encoding.UTF8);
xmlw.WriteStartDocument();            
xmlw.WriteStartElement("examtimes");
xmlw.WriteStartElement("Starttime");
xmlw.WriteString(DateTime.Now.AddHours(0).ToString());
xmlw.WriteEndElement();
xmlw.WriteStartElement("Changetime");
xmlw.WriteString(DateTime.Now.AddHours(0).ToString());
xmlw.WriteEndElement();
xmlw.WriteStartElement("Endtime");
xmlw.WriteString(DateTime.Now.AddHours(1).ToString());
xmlw.WriteEndElement();
xmlw.WriteEndElement();
xmlw.WriteEndDocument();  
xmlw.Close();           

To edit the Xml nodes use the below code

XmlDocument doc = new XmlDocument(); 
doc.Load(@"C:\WINDOWS\Temp\exm.xml"); 
XmlNode root = doc.DocumentElement["Starttime"]; 
root.FirstChild.InnerText = "First"; 
XmlNode root1 = doc.DocumentElement["Changetime"]; 
root1.FirstChild.InnerText = "Second"; 
doc.Save(@"C:\WINDOWS\Temp\exm.xml"); 

Try this. It's C# code.

Fara

Answer 4

The XmlTextWriter is usually used for generating (not updating) XML content. When you load the xml file into an XmlDocument, you don't need a separate writer.

Just update the node you have selected and .Save() that XmlDocument.

Rainger