Develop Reference

How do I select a specific xmlnode and change it values

My xml looks like this....
<?xml version="1.0" encoding="utf-8"?>
<messwerte>
<messwert>
<tag>1</tag>
<niederschlag>46</niederschlag>
<temperatur>7,6</temperatur>
<druck>4,6</druck>
</messwert>
......
</messwerte>
Now, I wanna give a a specific day where I want to change "niederschlag" "temperatur" and "druck" and I tried this:
public static void WriteXML(int day, double[] mess, string path)
{
XmlDocument doc = new XmlDocument();
doc.Load(path);
XmlElement nieder = doc.SelectSingleNode("/messwerte/messwert" + Convert.ToString(day) + "/niederschlag") as XmlElement;
if (nieder != null)
{
nieder.InnerText = Convert.ToString(mess[0]);
}
}
And it wont work.
And I know it's baaaad and super basic but i cant get it to work.......

I would suggest the reason it won't work for you, is you're trying to do 2 different things with one xpath string.
First you have to find the messwert element with a tag element that has an InnerText value matching the day value you're passing in.
Once you've identified the right element you want to change the InnerText of the niederschlag element.
Even though writing this out makes it seem quite complicated, leveraging a LINQ query can simplify it tremendously:
public static void WriteXML(int day, double[] mess, string path)
{
XmlDocument doc = new XmlDocument();
doc.Load(path);
var nieder = (from XmlElement element in doc.GetElementsByTagName("messwert")
where element.SelectSingleNode("tag").InnerText == day.ToString()
select element).First().SelectSingleNode("niederschlag");
if (nieder != null)
{
nieder.InnerText = mess[0].ToString();
}
doc.Save(path);
}
This code assumes your data is strongly controlled and that you'll never be looking for a day that isn't there.
If this isn't the case you'll have to assign the query including the First() method to a temporary variable, and check if it's null.
Something like this should work:
public static void WriteXML(int day, double[] mess, string path)
{
XmlDocument doc = new XmlDocument();
doc.Load(path);
var messwert = (from XmlElement element in doc.GetElementsByTagName("messwert")
where element.SelectSingleNode("tag").InnerText == day.ToString()
select element).FirstOrDefault();
if(messwert == null)
{
throw new ArgumentException($"The day value, doesn't exist. the value passed is {day}");
}
var nieder = messwert.SelectSingleNode("niederschlag");
if (nieder != null)
{
nieder.InnerText = mess[0].ToString();
}
doc.Save(path);
}

XMLinvalide chars replacement C#

I have a string that is displayed in XML but in it I have some invalid chars like string
s = <root> something here <XMLElement>hello</XMLElement> somethig here too </root>
where XMLElement is a List like XMLElement = {"bold", "italic",...} .
What I need is to replace the < and </ if followed by any of the XMLElements to be replaced by > or < depending on the cases.
The <root> is to keep
I have tried so far some regEx
strAux = Regex.Replace(strAux, "bold=\"[^\"]*\"",
match => match.Value.Replace("<", "<").Replace(">", ">"));
or
List<string> startsWith = new List<string> { "<", "</"};
foreach(var stw in startsWith)
{
int nextLt = 0;
while ((nextLt = strAux.IndexOf(stw, nextLt)) != -1)
{
bool isMatch = strAux.Substring(nextLt + 1).StartsWith(BoldElement); // needs to ckeck all the XMLElements
//is element, leave it
if (isMatch)
{
//its not, replace
strAux = string.Format(#"{0}<{1}", strAux.Substring(0, nextLt), strAux.Substring(nextLt +1, strAux.Length - (nextLt + 1)));
}
nextLt++;
}
}
Also tried
XmlDocument doc = new XmlDocument();
XmlElement element = doc.CreateElement("root");
element.InnerText = strAux;
Console.WriteLine(element.OuterXml);
strAux = element.OuterXml.Replace("<root>", "").Replace("</root>", "");
return strAux; But it will repeat the `<root>` too
But nothing worked like I suposed. Is there any different ideias .Thanks

What you have is well-formed XML, so you can use the XML APIs to help you:
Using LINQ to XML (which is generally the better API):
var element = XElement.Parse(s);
element.Value = string.Concat(element.Nodes());
var result = element.ToString();
Or using the older XmlDocument API:
var doc = new XmlDocument();
doc.LoadXml(s);
var root = doc.DocumentElement;
root.InnerText = root.InnerXml;
var result = root.OuterXml;
The result for both is:
<root> something here <XMLElement>hello</XMLElement> somethig here too </root>
See this fiddle for a demo.

You should be using the XmlWriter class.
Sample from the documentation:
XmlWriterSettings settings = new XmlWriterSettings();
settings.OmitXmlDeclaration = true;
settings.ConformanceLevel = ConformanceLevel.Fragment;
settings.CloseOutput = false;
// Create the XmlWriter object and write some content.
MemoryStream strm = new MemoryStream();
XmlWriter writer = XmlWriter.Create(strm, settings);
writer.WriteElementString("someNode", "someValue");
writer.Flush();
writer.Close();
https://msdn.microsoft.com/en-us/library/system.xml.xmlwriter(v=vs.110).aspx

It sounds like your input is well-formed XML, but you want to escape some of the tags. The issue here is that there's no way for the code to know which tags are valid and which aren't.
One way to do this is to create a list of valid tags.
List<string> validTags = new List<string>() { "root", "..." };
Then use regex to pick out all instances of <tag> or </tag>and replace them if they're not in the list.
Another way which is faster and easier, but requires more information up front, is to create a list of tags which aren't valid.
List<string> invalidTags = new List<string>() { "XMLElement", "..." };
Simple string manipulation will do, now.
string s = GetYourXMLString();
invalidTags.ForEach(t => s = s.Replace($"</{t}>",$"<{t}>")
.Replace($"<{t}>",$"</{t}>"));
The second way should really only be used if you know which foreign tags are making (or will ever make) an appearance. If not the first approach should be used. One clever possibility is to dynamically create the list of valid tags using reflection or a data contract so that changes to the XML spec will be automatically reflected in your code.
For example, if each element is a property of an object, you might get the list like this:
var validTags = typeof(MyObjectType).GetProperties()
.Select(p => p.PropertyName)
.ToList();
Of course, the property names likely won't be the actual tag names, AND often you'll want to only include certain properties. So you make an attribute class to designate the desired properties (let's call it XMLTagName) and then you can do this:
var validTags = typeof(MyObjectType).GetProperties()
.Select(p => p.GetCustomAttribute<XMLTagName>()?.TagName)
.Where(tagName => tagName != null) //gets rid of properties that aren't tagged
.ToList();
Even with all that, you'll still committing the crime of string manipulation on raw XML. After all, the best real solution here is to figure out how to fix the incoming XML to actually contain the data you want. But if that's not a possibility, the above should do the job.

how to get value from xml by Linq

i was reading huge xml file of 5GB size by using the following code, and i was success to get the first element Testid but failed to get another element TestMin coming under different namespace
this is the xml i am having
which i am getting as null
.What is wrong here?
EDIT
GMileys answer giving error like The ':' character, hexadecimal value 0x3A, cannot be included in a name

The element es:qRxLevMin is a child element of xn:attributes, but it looks like you are trying to select it as a child of xn:vsDataContainer, it is a grandchild of that element. You could try changing the following:
var dataqrxlevmin = from atts in pin.ElementsAfterSelf(xn + "VsDataContainer")
select new
{
qrxlevmin = (string)atts.Element(es + "qRxLevMin"),
};
To this:
var dataqrxlevmin = from atts in pin.Elements(string.Format("{0}VsDataContainer/{1}attributes", xn, es))
select new
{
qrxlevmin = (string)atts.Element(es + "qRxLevMin"),
};
Note: I changed your string concatenation to use string.Format for readability purposes, either is technically fine to use, but string.Format is a better approach.

What about this approach?
XDocument doc = XDocument.Load(path);
XName utranCellName = XName.Get("UtranCell", "un");
XName qRxLevMinName = XName.Get("qRxLevMin", "es");
var cells = doc.Descendants(utranCellName);
foreach (var cell in cells)
{
string qRxLevMin = cell.Descendants(qRxLevMinName).FirstOrDefault();
// Do something with the value
}

try this code which is very similar to your code but simpler.
using (XmlReader xr = XmlReader.Create(path))
{
xr.MoveToContent();
XNamespace un = xr.LookupNamespace("un");
XNamespace xn = xr.LookupNamespace("xn");
XNamespace es = xr.LookupNamespace("es");
while (!xr.EOF)
{
if(xr.LocalName != "UtranCell")
{
xr.ReadToFollowing("UtranCell", un.NamespaceName);
}
if(!xr.EOF)
{
XElement utranCell = (XElement)XElement.ReadFrom(xr);
}
}
}

actually namespace was the culprit,what i did is first loaded the small section i am getting from.Readform method in to xdocument,then i removed all the namespace,then i took the value .simple :)

A better way to handle XML updation

I have a DataGridView control where some values are popluted.
And also I have an xml file. The user can change the value in the Warning Column of DataGridView.And that needs to be saved in the xml file.
The below program just does the job
XDocument xdoc = XDocument.Load(filePath);
//match the record
foreach (var rule in xdoc.Descendants("Rule"))
{
foreach (var row in dgRulesMaster.Rows.Cast<DataGridViewRow>())
{
if (rule.Attribute("id").Value == row.Cells[0].Value.ToString())
{
rule.Attribute("action").Value = row.Cells[3].Value.ToString();
}
}
}
//save the record
xdoc.Save(filePath);
Matching the grid values with the XML document and for the matched values, updating the needed XML attribute.
Is there a better way to code this?
Thanks

You could do something like this:
var rules = dgRulesMaster.Rows.Cast<DataGridViewRow>()
.Select(x => new {
RuleId = x.Cells[0].Value.ToString(),
IsWarning = x.Cells[3].Value.ToString() });
var tuples = from n in xdoc.Descendants("Rule")
from r in rules
where n.Attribute("id").Value == r.RuleId
select new { Node = n, Rule = r };
foreach(var tuple in tuples)
tuple.Node.Attribute("action").Value = tuple.Rule.IsWarning;
This is basically the same, just a bit more LINQ-y. Whether or not this is "better" is debatable. One thing I removed is the conversion of IsWarning first to string, then to int and finally back to string. It now is converted to string once and left that way.

XPath allows you to target nodes in the xml with alot of power. Microsoft's example of using the XPathNavigator to modify an XML file is as follows:
XmlDocument document = new XmlDocument();
document.Load("contosoBooks.xml");
XPathNavigator navigator = document.CreateNavigator();
XmlNamespaceManager manager = new XmlNamespaceManager(navigator.NameTable);
manager.AddNamespace("bk", "http://www.contoso.com/books");
foreach (XPathNavigator nav in navigator.Select("//bk:price", manager))
{
if (nav.Value == "11.99")
{
nav.SetValue("12.99");
}
}
Console.WriteLine(navigator.OuterXml);
Source: http://msdn.microsoft.com/en-us/library/zx28tfx1(v=vs.80).aspx

How do I retrieve all data from an XML file?

I used this code for retrieving specific value from the XML file.Now i want to retrieve all the data which are present in the XML file .Can anybody help me to find out the solution?
StorageFile xmlFile = await Windows.ApplicationModel.Package.Current.InstalledLocation.GetFileAsync("Content1.xml");
XmlDocument xmlDoc;
xmlDoc = await XmlDocument.LoadFromFileAsync(xmlFile);
System.Xml.Linq.XDocument duc = System.Xml.Linq.XDocument.Parse(xmlDoc.GetXml());
var query=
from Date in duc.Root.Elements("Serial")
where Date.Attribute("No").Value=="1"
from Current in Date.Elements("Current")
select new {
NarratedBy=Current.Attribute("NarratedBy").Value,
value=Current.Attribute("Date").Value
};
foreach(var Date in query) {
System.Diagnostics.Debug.WriteLine("{0}\t{1}", Date.NarratedBy, Date.value);
}

You already have whole XML document loaded into duc variable.
That line is responsible for that:
System.Xml.Linq.XDocument duc = System.Xml.Linq.XDocument.Parse(xmlDoc.GetXml());

then you can just retrieve your XDocument details for example into a string variable with an XDocument extension ToString()

You have all data already:
xmlDoc = await XmlDocument.LoadFromFileAsync(xmlFile); // data loadded
System.Xml.Linq.XDocument duc = System.Xml.Linq.XDocument.Parse(xmlDoc.GetXml()); // data parsed
===================
Here is a sample code how you may do it. It is fully functional (using local string xml instead of your file) so you may run it. I added only three attributes but you may add as many as you want.
class Program {
static void Main(string[] args) {
// this is a sample string. Use your file instead
string s = "<catalog>" +
"<book id=\"bk101\" author=\"Gambardella, Matthew\" title=\"XML Developer's Guide\" genre=\"Computer\"/>" +
"<book id=\"bk102\" author=\"Ralls, Kim\" title=\"Midnight Rain\" genre=\"Fantasy\"/>" +
"</catalog>";
XmlDocument xdoc = new XmlDocument();
xdoc.LoadXml(s); // here we load data
// here we get attributes. I have three, you will add three more. Also you may want to use string array instead of variables
foreach (XmlNode task in xdoc.DocumentElement.ChildNodes)
{
string author = task.Attributes["author"].InnerText;
string title = task.Attributes["title"].InnerText;
string genre = task.Attributes["genre"].InnerText;
}
}
}