Develop Reference

Cannot change XmlDocument value?

I have a simple function which will simply change and read the value.
void ParseXml(string XmlFile)
{
string totalval = "";
XmlDocument xmldoc = new XmlDocument();
xmldoc.Load(new StringReader(XmlFile));
string xmlPathPattern = "//name";
XmlNodeList mynodelist = xmldoc.SelectNodes(xmlPathPattern);
foreach (XmlNode node in mynodelist)
{
XmlNode name = node.FirstChild;
name.Value = "asd";//here I am trying to change value
totalval = totalval + "Name=" + name.OuterXml + "\n";
}
xmldoc.Save(XmlFile);
print(totalval);
}
This is my .xml file.
<name>John</name>
I can successfully read the value but it is not changing the value from .xml file.After running the program it must be like this
<name>asd</name> .
Where is my mistake ?

Obviously, the XMLFile is not a file path, it is xml string. So, you should define a valid path to save it.
xmldoc.Save("samplefile.xml");
or if you want to set the XmlFile variable with modified xml;
XmlFile = xmldoc.OuterXml;
Complete codes look like;
void ParseXml(string XmlFile)
{
string totalval = "";
XmlDocument xmldoc = new XmlDocument();
xmldoc.Load(new StringReader(XmlFile));
string xmlPathPattern = "//name";
XmlNodeList mynodelist = xmldoc.SelectNodes(xmlPathPattern);
foreach (XmlNode node in mynodelist)
{
XmlNode name = node.FirstChild;
name.Value = "asd";//here I am trying to change value
totalval = totalval + "Name=" + name.OuterXml + "\n";
}
//XmlFile = xmldoc.OuterXml;
xmldoc.Save("samplefile.xml");
print(totalval);
}

If I'm not wrong - you need to fire disposable to save stream. Easiest way - wrap with using
void ParseXml(string XmlFile)
{
string totalval = "";
using(XmlDocument xmldoc = new XmlDocument())
{
xmldoc.Load(new StringReader(XmlFile));
string xmlPathPattern = "//name";
XmlNodeList mynodelist = xmldoc.SelectNodes(xmlPathPattern);
foreach (XmlNode node in mynodelist)
{
XmlNode name = node.FirstChild;
name.Value = "asd";//here I am trying to change value
totalval = totalval + "Name=" + name.OuterXml + "\n";
}
xmldoc.Save(XmlFile);
print(totalval);
}
}

Get Innertext from an XML string which has only one node without looping

I have an XML string which looks like below
<?xml version="1.0" encoding="Windows-1252"?><Product><ID>0701161476416</ID><UNIQUE_ID>test26051602</UNIQUE_ID><STATUS>DONE</STATUS></Product>
It is know that my XML string will always has a single node ans so I do not want to look, instead I would like to get Unique_ID and Status inner values without looping.
May I know a better way to do it and I do have the below code which actually loops through each node
XmlDocument xm = new XmlDocument();
xm.LoadXml(XML_STRING);
XmlNodeList xnList = xm.SelectNodes("/Product/Product");
foreach (XmlNode xn in xnList)
{
string uniqueID = xn["UNIQUE_ID"].InnerText;
string status = xn["STATUS"].InnerText;
}

There is SelectSingleNode() which you can use for this purpose :
XmlNode product = xm.SelectSingleNode("/Product/Product");
string uniqueID = product["UNIQUE_ID"].InnerText;
string status = product["STATUS"].InnerText;
Or, if Product is the root element, then you can access it from DocumentElement property of the XmlDocument :
XmlNode product = xm.DocumentElement;
string uniqueID = product["UNIQUE_ID"].InnerText;
string status = product["STATUS"].InnerText;

If you have more than one product try xml linq
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
string xml =
"<?xml version=\"1.0\" encoding=\"Windows-1252\"?>" +
"<Products>" +
"<Product>" +
"<ID>0701161476416</ID>" +
"<UNIQUE_ID>test26051603</UNIQUE_ID>" +
"<STATUS>DONE</STATUS>" +
"</Product>" +
"<Product>" +
"<ID>0701161476417</ID>" +
"<UNIQUE_ID>test26051604</UNIQUE_ID>" +
"<STATUS>DONE</STATUS>" +
"</Product>" +
"<Product>" +
"<ID>0701161476418</ID>" +
"<UNIQUE_ID>test26051605</UNIQUE_ID>" +
"<STATUS>DONE</STATUS>" +
"</Product>" +
"</Products>";
XDocument doc = XDocument.Parse(xml);
var results = doc.Descendants("Product").Select(x => new
{
id = (long)x.Element("ID"),
uniqueID = (string)x.Element("UNIQUE_ID"),
status = (string)x.Element("STATUS")
}).ToList();
}
}
}

This could work, but I guess there is a better solution:
XDocument xm = XDocument.Parse(XML_STRING);
var product = xm.Element("Product").Element("Product");
string uniqueID = product.Element("UNIQUE_ID").Value;
string status = product.Element("STATUS").Value;

Your SelectNodes line seemed wrong for the sample Xml.
XmlNodeList xnList = xm.SelectNodes("/Product");
if (xnList.Count > 0)
{
string uniqueID = xnList[0]["UNIQUE_ID"].InnerText;
string status = xnList[0]["STATUS"].InnerText;
}

Ignore the value of an empty Attributes in the element LINQ C#

I'm trying to retrieve values from an XML file and I find some values are empty.
textBox6, textBox7, textBox14 corresponding element attribute values are empty/null. The error message is Null reference error was unhanded . How can fix this??
private void DisplayFile(string path)
{
var doc = XDocument.Load(path);
var ns = doc.Root.GetDefaultNamespace();
var conn = doc.Root.Element(ns + "connection");
textBox1.Text = conn.Element(ns + "sourceId").Value;
var doc1 = XDocument.Load(path);
var ns1 = doc.Root.GetDefaultNamespace();
var conn1 = doc.Root.Element(ns1 + "connectionContext");
}

If a given element is not present in the XML foo.Element("someNode") will return null. When accessing .Value you get a NullReferenceException.
In order to avoid this NullReferenceException you need to check if the element is not null.
Example with contextType:
var contextType = conn1.Element(ns + "contextType");
if (contextType != null)
{
textBox15.Text = contextType.Value;
}
Update:
You try to load the connectionContext node from the root element. But this node is a child of the source node. You need to first load this node:
var source = doc.Root.Element(ns + "source");
var conn1 = source.Element(ns + "connectionContext");

I find your problem try this (i use string cause didn't want to make textboxes)
var doc = XDocument.Load("C:\\Test\\stovfl.xml");
var ns = doc.Root.GetDefaultNamespace();
var conn = doc.Root.Element(ns + "connection");
string s1 = conn.Element(ns + "sourceId").Value;
string s2 = conn.Element(ns + "username").Value;
var conn1 = doc.Root.Element("source");
var conn2 = conn1.Element("connectionContext");
string s6 = conn2.Element(ns + "organization").Value;
string s7 = conn2.Element(ns + "field").Value;
string s14 = conn2.Element(ns + "description").Value;
string s15 = conn2.Element(ns + "contextType").Value;
problem was that you have connectionContext in source, but try to find it in Root

how to read and change the xml file in C#

Thank you very much for reading my question.
and this is my xml file. (for node Songs, many childNodes named Song)
<?xml version="1.0" encoding="utf-8" ?>
<xmlData>
<version>1.0</version>
<Songs>
<Song>
<artist>mic</artist>
<track>2</track>
<column>happy</column>
<date>14</date>
</Song>
<Song>
<artist>cool</artist>
<track>2</track>
<column>work</column>
<date>4</date>
</Song>
</Songs>
</xmlData>
reading xml, i use the following code:
XmlDocument doc = new XmlDocument();
doc.Load(xmlFilePath);
XmlNode versionNode = doc.SelectSingleNode(#"/xmlData/version");
Console.WriteLine(versionNode.Name + ":\t" + versionNode.InnerText);
XmlNode SongsNode = doc.SelectSingleNode(#"/xmlData/Songs");
Console.WriteLine(SongsNode.Name + "\n");
XmlDocument docSub = new XmlDocument();
docSub.LoadXml(SongsNode.OuterXml);
XmlNodeList SongList = docSub.SelectNodes(#"/Songs/Song");
if (SongList != null)
{
foreach (XmlNode SongNode in SongList)
{
XmlNode artistDetail = SongNode.SelectSingleNode("artist");
Console.WriteLine(artistDetail.Name + "\t: " + artistDetail.InnerText);
XmlNode trackDetail = SongNode.SelectSingleNode("track");
Console.WriteLine(trackDetail.Name + "\t: " + trackDetail.InnerText);
XmlNode columnDetail = SongNode.SelectSingleNode("column");
Console.WriteLine(columnDetail.Name + "\t: " + columnDetail.InnerText);
XmlNode dateDetail = SongNode.SelectSingleNode("date");
Console.WriteLine(dateDetail.Name + "\t: " + dateDetail.InnerText + "\n");
}
}
it seems working.
but how can i write the change to xml file?
maybe, i will change some childNode in Song, and may delete the whole chindNode by artist keyword.
is it possible such as this function
bool DeleteSongByArtist(string sArtist);
bool ChangeNodeInSong(string sArtist, string sNodeName, string value);
because the "Reading solution is "XmlDucoment", so it is better if "changing solution" by using "XmlDocument"
but, if you have better idea to read and change the xml file, please give me the sample code... and please don't write a name of solution such as "Ling to xml"...acutally, i do many testes, but failed.

Welcome to Stackoverflow!
You can change the nodes simply by setting a new .Value or in your case .InnerText.
Sample
// change the node
trackDetail.InnerText = "NewValue"
// save the document
doc.Save(xmlFilePath);
More Information
How To: Modify an Existing Xml File
MSDN - XmlDocument.Save Method

You need to use an XmlWriter. The easiest way to do it would be something like this...
using(XmlWriter writer = new XmlWriter(textWriter))
{
doc.WriteTo(writer);
}
Where textWriter is your initialized Text Writer.
Actually, forget that... the easiest way is to call...
doc.Save(xmlFilePath);
To delete an artist by artist name add the following method:
bool DeleteSongByArtist(XmlDocument doc, string artistName)
{
XmlNodeList SongList = doc.SelectNodes(#"/Songs/Song");
if (SongList != null)
{
for (int i = SongList.Count - 1; i >= 0; i--)
{
if (SongList[i]["artist"].InnerText == artistName && SongList[i].ParentNode != null)
{
SongList[i].ParentNode.RemoveChild(SongList[i]);
}
}
}
}
You probably want to clean it up a bit more to be more resilient. When you call it, change your initial code to be like this. Don't create the subDocument as you want to work with the entire XmlDocument.
XmlDocument doc = new XmlDocument();
doc.Load(xmlFilePath);
XmlNode versionNode = doc.SelectSingleNode(#"/xmlData/version");
Console.WriteLine(versionNode.Name + ":\t" + versionNode.InnerText);
XmlNode SongsNode = doc.SelectSingleNode(#"/xmlData/Songs");
Console.WriteLine(SongsNode.Name + "\n");
XmlNodeList SongList = doc.SelectNodes(#"/Songs/Song");
if (SongList != null)
{
foreach (XmlNode SongNode in SongList)
{
XmlNode artistDetail = SongNode.SelectSingleNode("artist");
Console.WriteLine(artistDetail.Name + "\t: " + artistDetail.InnerText);
XmlNode trackDetail = SongNode.SelectSingleNode("track");
Console.WriteLine(trackDetail.Name + "\t: " + trackDetail.InnerText);
XmlNode columnDetail = SongNode.SelectSingleNode("column");
Console.WriteLine(columnDetail.Name + "\t: " + columnDetail.InnerText);
XmlNode dateDetail = SongNode.SelectSingleNode("date");
Console.WriteLine(dateDetail.Name + "\t: " + dateDetail.InnerText + "\n");
}
}

You aren't able to save your changes because you made changes to an entirely new document!
You likely meant to do the following:
XmlNode SongsNode = doc.SelectSingleNode(#"/xmlData/Songs");
Console.WriteLine(SongsNode.Name + "\n");
// Don't make a new XmlDocument here! Use your existing one
XmlNodeList SongList = SongsNode.SelectNodes(#"/Song");
At this point SongList is still living inside doc. Now when you call:
doc.Save(xmlFilePath);
Your changes will be saved as you intended.
If you're looking to delete nodes that match certain criteria:
// Use XPath to find the matching node
XmlNode song = SongsNode.SelectSingleNode(#"/Song[artist='" + artist + "']");
// Remove it from its Parent
SongsNode.RemoveChild(song);
If you're looking to add a new node:
// Create the new nodes using doc
XmlNode newSong = doc.CreateElement("Song");
XmlNode artist = doc.CreateElement("artist");
artist.InnerText = "Hello";
// Begin the painstaking process of creation/appending
newSong.AppendChild(artist);
// rinse...repeat...
// Finally add the new song to the SongsNode
SongsNode.AppendChild(newSong);

You could do
XmlNodeList SongList = doc.SelectNodes(#"//Songs/Song");
The // tells it to select the Songs node anywhere in document. This is better than
doc.SelectNodes(#"/document/level1/music/Songs")
Note that the above statement is oviously not for your xml, but to prove a point about //
Using // removes the need for your docSub document and SongsNode element.
To add then delete a song, just use the following
XmlDocument doc = new XmlDocument();
XmlElement ea = doc.SelectSingleNode("//songs");
XmlElement el = doc.CreateElement("song");
XmlElement er;
ea.AppendChild(el);
//doing my work with ea
//you could use innerxml.
el.InnerXml = "<artist>Judas Priest</artist><track>7</track><column>good</column><date>1</date>";
//or you can treat each node as above
er = doc.CreateElement("Name");
el.AppendChild(er);
er.InnerText = "The Ripper";
//but you don't nead this song any more?
ea.RemoveChild(el);
//so it's gone.
And thats all there is to it.

please don't write a name of solution such as "Ling to xml"...acutally, i do many testes, but failed.
Still I think, this is a very good time to start to use Linq2Xml. If you don't like it, just ignore.
XDocument xDoc = XDocument.Load(new StringReader(xml));
//Load Songs
var songs = xDoc.Descendants("Song")
.Select(s => new
{
Artist = s.Element("artist").Value,
Track = s.Element("track").Value,
Column = s.Element("column").Value,
Date = s.Element("date").Value,
})
.ToArray();
//Delete Songs
string songByArtist="mic";
xDoc.Descendants("Song")
.Where(s => s.Element("artist").Value == songByArtist)
.Remove();
string newXml = xDoc.ToString();

How to obtain inner tags value in XML?

XDocument coordinates = XDocument.Load("http://feeds.feedburner.com/TechCrunch");
System.IO.StreamWriter StreamWriter1 = new System.IO.StreamWriter(DestFile);
XNamespace nsContent = "http://purl.org/rss/1.0/modules/content/";
string pchild = null;
foreach (var item in coordinates.Descendants("item"))
{
string link = item.Element("guid").Value;
//string content = item.Element(nsContent + "encoded").Value;
foreach (var child in item.Descendants(nsContent + "encoded"))
{
pchild = pchild + child.Element("p").Value;
}
StreamWriter1.WriteLine(link + Environment.NewLine + Environment.NewLine + pchild + Environment.NewLine);
}
StreamWriter1.Close();
If i use Commented line code (string content = item.Element(nsContent + "encoded").Value;) instead of inner for loop than it will fetch the value of <conten:encoded> element but it contains all links, images etc etc. And I want only text.
For that I have tried to use this filter (inner for loop) but its showing error :
Object reference not set to an instance of an object.
Please suggest me code so that I can store only text and remove all other links, <img> tags etc.

The content of item.Element(nsContent + "encoded").Value is html not xml. You should parse it accordingly, such as using Html Agility Pack
See the example below
string content = item.Element(nsContent + "encoded").Value;
HtmlAgilityPack.HtmlDocument doc = new HtmlAgilityPack.HtmlDocument();
doc.Load(new StringReader(content));
var text = String.Join(Environment.NewLine + Environment.NewLine,
doc.DocumentNode
.Descendants("p")
.Select(n => "\t" + System.Web.HttpUtility.HtmlDecode(n.InnerText))
);

Firstly, I would start by using a StringBuilder:
StringBuilder sb = new StringBuilder();
Then, I suspect that sometimes, the "child" doesn't have a "p" element, so you can check before using it:
foreach (var child in item.Descendants(nsContent + "encoded"))
{
if (child.Element("p") != null)
{
sb.Append(child.Element("p").Value);
}
}
StreamWriter1.WriteLine(link + Environment.NewLine + Environment.NewLine + sb.ToString() + Environment.NewLine);
Does that work for you?