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Modify xml with Xmldocument in C#

I am trying to edit the values of an xml document following the instructions found on another post here How to modify existing XML file with XmlDocument and XmlNode in C# .
here is my code
XmlDocument xml = new XmlDocument();
xml = xml.Load(#"https://www.aade.gr/sites/default/files/2020-09/SampleXML_1.1%20%20%28%CE%A4%CE%99%CE%9C-%CE%A0%CE%A9%CE%9B%CE%97%CE%A3%CE%97%CE%A3_%CE%91%CE%A5%CE%A4%CE%9F%CE%A4%CE%99%CE%9C%29%20.xml");
XmlNodeList aNodes = xml.SelectNodes("/InvoicesDoc/invoice/issuer/vatNumber");
foreach (XmlNode aNode in aNodes)
{
XmlAttribute vatAttribute = aNode.Attributes["vatNumber"];
vatAttribute.Value = "123456789";
}
xml.Save(#"C:\Users\Kostas\Desktop\mydata\infinal.xml");
My problem is that XmlNodeList aNodes will return empty; i have tried to change the xml.SelectNodes("/InvoicesDoc/invoice/issuer/vatNumber") to xml.SelectNodes("/InvoicesDoc/invoice/issuer") and all the way up to single xml.SelectNodes("/InvoicesDoc") but still XmlNodeList aNodes will return empty.
First attempts i loaded the XML doc from file and had the issue. Then i thought maybe something wrong with the file so changed the load of the file directly from the site provides this xml template i need to work on. Both options will load the file fine as i can see it when is saved but my changes will not complete since aNodes is empty and foreach loop will skip straight away.
What am i doing wrong?
thanks for your help in advance.
ps this is the xml i need to edit
https://www.aade.gr/sites/default/files/2020-09/SampleXML_1.1%20%20%28%CE%A4%CE%99%CE%9C-%CE%A0%CE%A9%CE%9B%CE%97%CE%A3%CE%97%CE%A3_%CE%91%CE%A5%CE%A4%CE%9F%CE%A4%CE%99%CE%9C%29%20.xml
Update: I just tried with another xlm found in microsoft example called books on https://learn.microsoft.com/en-us/previous-versions/windows/desktop/ms762271(v=vs.85)
XmlNodelist will also return null/empty when i look for /catalog/book . So the good side is that there is no problem with original xml file i need to edit and the bad side is that still i cannot figure out what i am doing wrong.

XmlNodeList aNodes returns null because the xml contains these namespace declarations:
<InvoicesDoc xmlns=\"http://www.aade.gr/myDATA/invoice/v1.0\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"
xsi:schemaLocation=\"http://www.aade.gr/myDATA/invoice/v1.0/InvoicesDoc-v0.6.xsd\"
xmlns:icls=\"https://www.aade.gr/myDATA/incomeClassificaton/v1.0\"
xmlns:ecls=\"https://www.aade.gr/myDATA/expensesClassificaton/v1.0\">
You need to manage your xml doing something like this:
XmlDocument xml = new XmlDocument();
xml.Load(#"https://www.aade.gr/sites/default/files/2020-09/SampleXML_1.1%20%20%28%CE%A4%CE%99%CE%9C-%CE%A0%CE%A9%CE%9B%CE%97%CE%A3%CE%97%CE%A3_%CE%91%CE%A5%CE%A4%CE%9F%CE%A4%CE%99%CE%9C%29%20.xml");
XmlNamespaceManager manager = new XmlNamespaceManager(xml.NameTable);
manager.AddNamespace("InvoicesDoc", "http://www.aade.gr/myDATA/invoice/v1.0");
//Example to get the root element
XmlNodeList root = xml.SelectNodes("/InvoicesDoc:InvoicesDoc", manager);
//Example to get the VatNumber tag
XmlNodeList aNodes =xml.SelectNodes("/InvoicesDoc:InvoicesDoc/InvoicesDoc:invoice/InvoicesDoc:issuer/InvoicesDoc:vatNumber", manager);

Generate XML in C# Using Specific XML Namespace

Target XML I am trying to achieve:
<Row><Data ss:Type="String">value</Data></Row>
Output I am currently getting:
<Row xmlns=""><Data Type="Number">0</Data></Row>
I am trying to create that target XML code using the System.Xml library, but the namespace prefix is not showing up when I create new elements. Snippet of the code that is generating the above output:
XmlElement eRow = xDoc.CreateElement("Row");
XmlElement eData = xDoc.CreateElement("Data");
XmlAttribute xAt = xDoc.CreateAttribute("ss", "Type", null);
xAt.Value = "Number";
eData.Attributes.Append(xAt);
eData.InnerText = "0";
eRow.AppendChild(eData);
I am trying to append this XML to a file that already exists. I have loaded the file as
XmlDocument xTemp = new XmlDocument();
xTemp.Load(templatePath);
and there are already namespaces in DocumentElement.Attributes that have already declared the prefix that I want to use: <Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet" xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet">. Essentially, I am trying to get the "ss" prefix to show up before "Type" like in the target I provided above. Additionally, the output is displaying xmlns="" as an attribute in the "Row" tag, something that I never added. I assume these are both issues with the namespace not being declared, but as mentioned above, it should already be declared in the original document that I loaded.
How can I generate the target XML code I want?

You have created your attribute xAt without specifying the namespace uri, which is equivalent to empty string namespace uri (see the corresponding MSDN doc here), that is certainly why you get the <Row xmlns="">
Actually you need to specify the exact namespace uri for it to work as you expect it.
Let me illustrate using the namespace uri you have given in your question (Illustration very similar to your initial code but might have a few small differences that you can easily modify).
String namespaceUri = "urn:schemas-microsoft-com:office:spreadsheet";
XmlDocument xDoc = new XmlDocument();
XmlElement workbook = xDoc.CreateElement("ss", "Workbook", namespaceUri);
XmlElement rows = xDoc.CreateElement("Rows");
At this step I can assume that I have an XmlDocument similar to what you have after initially loading your file. My XmlDocument has the workbook node as its DocumentElement, it uses the given prefix and namespace uri.
Now we can create the attribute:
var attribute = xDoc.CreateAttribute("ss", "Type", "urn:schemas-microsoft-com:office:spreadsheet");
attribute.Value = "String";
The namespace uri should be specified correctly otherwise it won't be correctly rendered. When this attribute is used, since the namespace it is refering to is found on the nesting element (workbook), it is not necessary to mention it again here, and the framework will automatically remove the reference to the namespace uri.
Now we can go ahead and create the Row and data elements and add the attribute to the collection of attributes of the Data element.
XmlElement eRow = xDoc.CreateElement("Row");
XmlElement eData = xDoc.CreateElement("Data");
eData.Attributes.Append(attribute);
eData.InnerText = "value";
eRow.AppendChild(eData);
rows.AppendChild(eRow);
workbook.AppendChild(rows);
xDoc.AppendChild(workbook);
We can then display the document, for example with:
Console.WriteLine(xDoc.OuterXml);
Result:
<ss:Workbook xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet"><Rows><Row><Data ss:Type="String">value</Data></Row></Rows></ss:Workbook>
I hope this helps.

How to change the data within elements in a XML file using C#?

I'm kind of new to XML files in C# ASP.NET. I have a XML in the below format:
<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<Installation>
<ServerIP>192.168.20.110</ServerIP>
<DB_Name>USTCKT1</DB_Name>
<Username>jorame</Username>
<Password>Cru$%e20</Password>
<Table_PreFix>TCK</Table_PreFix>
</Installation>
I need to change the values within each element. For example, when an user clicks I should be able to replace 192.168.20.110 with 192.168.1.12.
How can I accomplish this? Any help will be really appreciated.

You should look at using the methods in the XDocument class. http://msdn.microsoft.com/en-us/library/bb301598.aspx
Specifically look at the methods: Load(string) - to load an XML file, Element() - to access a specific element and Save(string) - to save the XML document. The page on Element() has some sample code which can help.
http://msdn.microsoft.com/en-us/library/system.xml.linq.xcontainer.element.aspx

You can do something like this using the XDocument class:
XDocument doc = XDocument.Load(file.xml);
doc.Element("Installation").Element("ServerIP").Value = "192.168.1.12";
//Update the rest of the elements
doc.Save(file.xml);
More Details
If you run into namespace issues when selecting your elements you will need to include the xml namespace in the XElement selectors eg doc.Element(namspace + "Installation")

In general, you can do it in the following steps:
Create a new XmlDocument object and load the content. The content might be a file or string.
Find the element that you want to modify. If the structure of your xml file is too complex, you can use xpath you find what you want.
Apply your modification to that element.
Update your xml file.
Here is a simple demo:
XmlDocument xmlDoc = new XmlDocument();
xmlDoc.Load("file.xml"); // use LoadXml(string xml) to load xml string
string path = "/Installation/ServerIP";
XmlNode node = xmlDoc.SelectSingleNode(path); // use xpath to find a node
node.InnerText = "192.168.1.12"; // update node, replace the inner text
xmlDoc.Save("file.xml"); // save updated content
Hope it's helpful.

Geotagging in xml can't be use in c#

I'm new in twitter api and now i try to get the geotagging from xml data of twitter
my code for get geo code is
XmlNode eNode = xn.SelectSingleNode("coordinates/georss:point");
error is
XPathException was unhandle by user code
-Namespace Manager or XsltContext needed. This query has a prefix, variable, or user-defined function.
but for other data suchas name, text or id is work fine to get it
thanks for your help ^^

It speaks the truth. Simply declare an XmlNamespaceManager, and tell it what uri "georss" refers to:
XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
nsmgr.AddNamespace("georss", "http://www.georss.org/georss");
and pass ns into the SelectSingleNode call:
XmlNode eNode = xn.SelectSingleNode("coordinates/georss:point", nsmgr);
You should be able to find the uri from the xmlns alias declaration at the top of the xml (edit: #dtb found it already).

Query an XmlDocument without getting a 'Namespace prefix is not defined' problem

I've got an Xml document that both defines and references some namespaces. I load it into an XmlDocument object and to the best of my knowledge I create a XmlNamespaceManager object with which to query Xpath against. Problem is I'm getting XPath exceptions that the namespace "my" is not defined. How do I get the namespace manager to see that the namespaces I am referencing are already defined. Or rather how do I get the namespace definitions from the document to the namespace manager.
Furthermore tt strikes me as strange that you have to provide a namespace manager to the document which you create from the documents nametable in the first place. Even if you need to hardcode manual namespaces why can't you add them directly to the document. Why do you always have to pass this namespace manager with every single query? What can't XmlDocument just know?
Code:
XmlDocument xmlDoc = new XmlDocument();
xmlDoc.Load(programFiles + #"Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\FEATURES\HfscBookingWorkflow\template.xml");
XmlNamespaceManager ns = new XmlNamespaceManager(xmlDoc.NameTable);
XmlNode referenceNode = xmlDoc.SelectSingleNode("/my:myFields/my:ReferenceNumber", ns);
referenceNode.InnerXml = this.bookingData.ReferenceNumber;
XmlNode titleNode = xmlDoc.SelectSingleNode("/my:myFields/my:Title", ns);
titleNode.InnerXml = this.bookingData.FamilyName;
Xml:
<?xml version="1.0" encoding="UTF-8" ?>
<?mso-infoPathSolution name="urn:schemas-microsoft-com:office:infopath:Inspection:-myXSD-2010-01-15T18-21-55" solutionVersion="1.0.0.104" productVersion="12.0.0" PIVersion="1.0.0.0" ?>
<?mso-application progid="InfoPath.Document" versionProgid="InfoPath.Document.2"?>
<my:myFields xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xhtml="http://www.w3.org/1999/xhtml" xmlns:my="http://schemas.microsoft.com/office/infopath/2003/myXSD/2010-01-15T18:21:55" xmlns:xd="http://schemas.microsoft.com/office/infopath/2003">
<my:DateRequested xsi:nil="true" />
<my:DateVisited xsi:nil="true" />
<my:ReferenceNumber />
<my:FireCall>false</my:FireCall>
Update:
ns.AddNamespace("xsi", "http://www.w3.org/2001/XMLSchema-instance");
ns.AddNamespace("xhtml", "http://www.w3.org/1999/xhtml");
ns.AddNamespace("xd", "http://schemas.microsoft.com/office/infopath/2003");
ns.AddNamespace("my", "http://schemas.microsoft.com/office/infopath/2003/myXSD/2010-01-15T18:21:55");
This does the job, but it mean's I have to hard code to this particular xml schema. This schema represents an infopath form template. In particular the my namespace url will be different for every form template so I really don't want to hardcode this. It would be nice to find a clean way to get this namespace from the xml without resorting to RegEx.
I was hoping that the XmlNamespaceManager would just sort of pick up the namespace definitions form the NameTable. I mean their in the Xml but I still have to define them.

ns.AddNamespace("xsi", "http://www.w3.org/2001/XMLSchema-instance");
ns.AddNamespace("xhtml", "http://www.w3.org/1999/xhtml");
ns.AddNamespace("xd", "http://schemas.microsoft.com/office/infopath/2003");
ns.AddNamespace("my", "http://schemas.microsoft.com/office/infopath/2003/myXSD/2010-01-15T18:21:55");
This does the job, but it mean's I have to hard code to this particular xml schema. This schema represents an infopath form template. In particular the my namespace url will be different for every form template so I really don't want to hardcode this. It would be nice to find a clean way to get this namespace from the xml without resorting to Regex.
I was hoping that the XmlNamespaceManager would just sort of pick up the namespace definitions form the NameTable. I mean their in the Xml but I still have to define them.

Here is the answer to the "What can't XmlDocument just know?" question.
NameTable is just an optimization for storing names. It has actually nothing to do with namespaces.
And even if XmlNamespaceManager could infer all namespaces and prefixes from XML doc that won't help in general case because of XML namespaces nature, e.g. what would XmlNamespaceManager map "my" prefix in this case:
<root>
<foo xmlns:my="blah"/>
<foo xmlns:my="balh-blah-blah"/>
</root>

Have you defined "my" in the namespace-manager?
ns.AddNamespace("my", "http://schemas.microsoft.com/office/infopath/2003/myXSD/2010-01-15T18:21:55");
Or better - choose something that is unlikely to conflict. It does seem odd that it didn't pick it up from the name-table, though.

For me with InfoPath 2007 this solved the problem
static public XmlNamespaceManager GetNameSpaceManager(this XmlDocument document)
{
XmlNamespaceManager xmlNamespaceManager = new XmlNamespaceManager(document.NameTable);
xmlNamespaceManager.AddNamespace("xsi", "http://www.w3.org/2001/XMLSchema-instance");
xmlNamespaceManager.AddNamespace("dfs", "http://schemas.microsoft.com/office/infopath/2003/dataFormSolution");
xmlNamespaceManager.AddNamespace("d", "http://schemas.microsoft.com/office/infopath/2003/ado/dataFields");
xmlNamespaceManager.AddNamespace("my", "http://schemas.microsoft.com/office/infopath/2003/myXSD/2012-03-29T06:28:28");
xmlNamespaceManager.AddNamespace("xd", "http://schemas.microsoft.com/office/infopath/2003");
return xmlNamespaceManager;
}