I am trying to create a simple XML file, but I am getting the exception
Object reference not set to an instance of an object
at this part:
doc.Root.Add(persons);
What am I doing wrong?
XDocument doc = new XDocument(new XDeclaration("1.0", "utf-8", null));
XElement persons = new XElement("Persons");
XElement[] el ={new XElement("PersonInfo",new XAttribute("ID",1),
new XElement("Name","ali"),
new XElement("Phone","222222"))
};
persons.Add(el);
doc.Add(persons);
doc.Save("PhoneBook.xml", SaveOptions.None);
Response.Write("ok");
}
You should just use:
doc.Add(persons);
Then you will get this XML:
<Persons>
<PersonInfo ID="1">
<Name>ali</Name>
<Phone>222222</Phone>
</PersonInfo>
</Persons>
An empty XDocument has no Root. That's why you get a NullReferenceException when you try to access it.
Related
How to parse the xml file?
<?xml version="1.0" encoding="UTF-8"?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
<sitemap>
<loc>link</loc>
<lastmod>2011-08-17T08:23:17+00:00</lastmod>
</sitemap>
<sitemap>
<loc>link</loc>
<lastmod>2011-08-18T08:23:17+00:00</lastmod>
</sitemap>
</sitemapindex>
I am new to XML, I tried this, but it seems to be not working :
XmlDocument xml = new XmlDocument(); //* create an xml document object.
xml.Load("sitemap.xml");
XmlNodeList xnList = xml.SelectNodes("/sitemapindex/sitemap");
foreach (XmlNode xn in xnList)
{
String loc= xn["loc"].InnerText;
String lastmod= xn["lastmod"].InnerText;
}
The problem is that the sitemapindex element defines a default namespace. You need to specify the namespace when you select the nodes, otherwise it will not find them. For instance:
XmlDocument xml = new XmlDocument();
xml.Load("sitemap.xml");
XmlNamespaceManager manager = new XmlNamespaceManager(xml.NameTable);
manager.AddNamespace("s", "http://www.sitemaps.org/schemas/sitemap/0.9");
XmlNodeList xnList = xml.SelectNodes("/s:sitemapindex/s:sitemap", manager);
Normally speaking, when using the XmlNameSpaceManager, you could leave the prefix as an empty string to specify that you want that namespace to be the default namespace. So you would think you'd be able to do something like this:
// WON'T WORK
XmlDocument xml = new XmlDocument();
xml.Load("sitemap.xml");
XmlNamespaceManager manager = new XmlNamespaceManager(xml.NameTable);
manager.AddNamespace("", "http://www.sitemaps.org/schemas/sitemap/0.9"); //Empty prefix
XmlNodeList xnList = xml.SelectNodes("/sitemapindex/sitemap", manager); //No prefixes in XPath
However, if you try that code, you'll find that it won't find any matching nodes. The reason for this is that in XPath 1.0 (which is what XmlDocument implements), when no namespace is provided, it always uses the null namespace, not the default namespace. So, it doesn't matter if you specify a default namespace in the XmlNamespaceManager, it's not going to be used by XPath, anyway. To quote the relevant paragraph from the Official XPath Specification:
A QName in the node test is expanded into an expanded-name using the
namespace declarations from the expression context. This is the same
way expansion is done for element type names in start and end-tags
except that the default namespace declared with xmlns is not used: if
the QName does not have a prefix, then the namespace URI is null (this
is the same way attribute names are expanded). It is an error if the
QName has a prefix for which there is no namespace declaration in the
expression context.
Therefore, when the elements you are reading belong to a namespace, you can't avoid putting the namespace prefix in your XPath statements. However, if you don't want to bother putting the namespace URI in your code, you can just use the XmlDocument object to return the URI of the root element, which in this case, is what you want. For instance:
XmlDocument xml = new XmlDocument();
xml.Load("sitemap.xml");
XmlNamespaceManager manager = new XmlNamespaceManager(xml.NameTable);
manager.AddNamespace("s", xml.DocumentElement.NamespaceURI); //Using xml's properties instead of hard-coded URI
XmlNodeList xnList = xml.SelectNodes("/s:sitemapindex/s:sitemap", manager);
Sitemap has 2 sub nodes "loc" and "lastmod". The nodes that you are accessing are "name" and "url". that is why you are not getting any result. Also in your XML file the last sitemap tag is not closed properly with a corresponding Kindly try xn["loc"].InnerText and see if you get the desired result.
I would definitely use LINQ to XML instead of the older XmlDocument based XML API. You can accomplish what you are looking to do using the following code. Notice, I changed the name of the element that I am trying to get the value of to 'loc' and 'lastmod', because this is what is in your sample XML ('name' and 'url' did not exist):
XElement element = XElement.Parse(XMLFILE);
IEnumerable<XElement> list = element.Elements("sitemap");
foreach (XElement e in list)
{
String LOC= e.Element("loc").Value;
String LASTMOD = e.Element("lastmod").Value;
}
I have a url in xml format.
Sample xml file format is as following:
<shows>
<show>
<eventID>10025</eventID>
<name>MARCH Barrel</name>
<ticketURL></ticketURL>
<venue>
<venueID>3648</venueID>
<name>Double Barrel</name>
<address>3770 Las Vegas Blvd. South</address>
<address2></address2>
<city>Las Vegas</city>
<state>NV</state>
<zipcode>89109</zipcode>
<country>US</country>
</venue>
</show>
</shows>
Question:
How, is it possible to store venueID & name in sql server 2008 using C#, as I have a table which contain this type of field ?
You can store information in SQL Server XML type field. Following article contains complete information for how to use XML datatype in sql server.
https://www.simple-talk.com/sql/learn-sql-server/working-with-the-xml-data-type-in-sql-server/
SQL Server 2005 and up have a datatype called "XML" which you can store XML in - untyped or typed with a XSD schema.
You can basically fill columns of type XML from an XML literal string, so you can easily just use a normal INSERT statement and fill the XML contents into that field.
OR
You can use the function OPENXML and stored procedure sp_xml_preparedocument to easily convert your XML into rowsets.
EDIT: Try This
String xmlFile = #" <shows>
<show>
<eventID>10025</eventID>
<name>MARCH Barrel</name>
<ticketURL></ticketURL>
<venue>
<venueID>3648</venueID>
<name>Double Barrel</name>
<address>3770 Las Vegas Blvd. South</address>
<address2></address2>
<city>Las Vegas</city>
<state>NV</state>
<zipcode>89109</zipcode>
<country>US</country>
</venue>
</show>
</shows>";
DataSet ds = ConvertXMLToDataSet(xmlFile);
foreach (DataTable dt in ds.Tables)
{
//get Your Tables here
}
and Method:
public static DataSet ConvertXMLToDataSet(string xmlData)
{
StringReader stream = null;
XmlTextReader reader = null;
try
{
DataSet xmlDS = new DataSet();
stream = new StringReader(xmlData);
// Load the XmlTextReader from the stream
reader = new XmlTextReader(stream);
xmlDS.ReadXml(reader);
return xmlDS;
}
catch
{
return null;
}
finally
{
if (reader != null) reader.Close();
}
}
first post. I hope it meets with the rules of asking questions.
I'm in a bit of bother with an xml document (its an API returned Xml). Now it uses a multitude of internet (http based) security measures which I have worked thru and I am now able to return the the top tier of nodes that are not nested.
however there are a few nodes which are nested under these and I need to return some of these values.
I'm set on using XMLDocument to do this, and I'm not interested in using XPath.
I should also note that I'm using the .Net 4.5 environment.
Example XML
<?xml version="1.0" encoding="utf-8"?>
<results>
<Info xmlns="http://xmlns.namespace">
<title>This Title</title>
<ref>
<SetId>317</SetId>
</ref>
<source>
<name>file.xxx</name>
<type>thisType</type>
<hash>cc7b99599c1bebfc4b8f12e47aba3f76</hash>
<pers>65.97602</pers>
<time>02:20:02.8527777</time>
</source>
....... Continuation which is same as above
Ok so above is the Xml that gets returned from the API, now, I can return title node no problem. What I would also like to return is any of the node values in the Element, for example the pers node value. But I only want to return one (as there are many in the existing xml further down)
Please note that there is an xmlns in the Info node which may not be allowing me to return the values.
So here is my code
using (var response = (HttpWebResponse) request.GetResponse())
{
//Get the response stream
using (Stream stream = response.GetResponseStream())
{
if (stream != null)
{
var xDoc = new XmlDocument();
var nsm = new XmlNamespaceManager(xDoc.NameTable);
nsm.AddNamespace("ns", XmlNamespace);
//Read the response stream
using (XmlReader xmlReader = XmlReader.Create(stream))
{
// This is straight forward, we just need to read the XML document and return the bits we need.
xDoc.Load(xmlReader);
XmlElement root = xDoc.DocumentElement;
var cNodes = root.SelectNodes("/results/ns:Info", nsm);
//Create a new instance of Info so that we can store any data found in the Info Properties.
var info = new Info();
// Now we have a collection of Info objects
foreach (XmlNode node in cNodes)
{
// Do some parsing or other relevant filtering here
var title = node["title"];
if (title != null)
{
info.Title = title.InnerText;
_logger.Info("This is the title returned ############# {0}", info.Title);
}
//This is the bit that is killing me as i can't return the any values in the of the sub nodes
XmlNodeList sourceNodes = node.SelectNodes("source");
foreach (XmlNode sn in sourceNodes)
{
XmlNode source = sn.SelectSingleNode("source");
{
var pers = root["pers"];
if (pers != null) info.pers = pers.InnerText;
_logger.Info("############FPS = {0}", info.pers);
}
}
}
}
Thanks in advance for any help
So I finally figured it out.
Here is the code that gets the subnodes. Basically I wasn't using my namespace identifier or my namespace for returning subnodes within the "Source" node.
For anybody else in this situation,
When you declare your name space there are to parts to it, a namespace identifier which is anything you want it to be in my case I chose "ns" and then the actual namespace in the XML file which is prefixed by xmlns and will contain something like for example: "http://xmlns.mynamespace".
So when searching subnodes inside the top level you need to declare these namespaces for the main node of the subnode you want to get.
// get the <source> subnode using the namespace to returns all <source> values
var source = node.SelectSingleNode("ns:source", nsm);
if (source != null)
{
info.SourceType = source["type"].InnerText;
info.Pers = source["pers"].InnerText;
_logger.Info("This SourceNode is {0}", info.SourceType);
_logger.Info("This PersNode is {0}", info.FramesPerSecond);
}
I hope this helps somebody else that's chasing their tails as I have.
Thanks
I'm having some difficulty with using NVelocity in an ASP.NET MVC application. I'm using it as a way of generating emails.
As far as I can make out the details I'm passing are all correct, but it fails to load the template.
Here is the code:
private const string defaultTemplatePath = "Views\\EmailTemplates\\";
...
velocityEngine = new VelocityEngine();
basePath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, defaultTemplatePath);
ExtendedProperties properties = new ExtendedProperties();
properties.Add(RuntimeConstants.RESOURCE_LOADER, "file");
properties.Add(RuntimeConstants.FILE_RESOURCE_LOADER_PATH, basePath);
velocityEngine.Init(properties);
The basePath is the correct directory, I've pasted the value into explorer to ensure it is correct.
if (!velocityEngine.TemplateExists(name))
throw new InvalidOperationException(string.Format("Could not find a template named '{0}'", name));
Template result = velocityEngine.GetTemplate(name);
'name' above is a valid filename in the folder defined as basePath above. However, TemplateExists returns false. If I comment that conditional out and let it fail on the GetTemplate method call the stack trace looks like this:
at NVelocity.Runtime.Resource.ResourceManagerImpl.LoadResource(String resourceName, ResourceType resourceType, String encoding)
at NVelocity.Runtime.Resource.ResourceManagerImpl.GetResource(String resourceName, ResourceType resourceType, String encoding)
at NVelocity.Runtime.RuntimeInstance.GetTemplate(String name, String encoding)
at NVelocity.Runtime.RuntimeInstance.GetTemplate(String name)
at NVelocity.App.VelocityEngine.GetTemplate(String name)
...
I'm now at a bit of an impasse. I feel that the answer is blindingly obvious, but I just can't seem to see it at the moment.
Have you considered using Castle's NVelocityTemplateEngine?
Download from the "TemplateEngine Component 1.1 - September 29th, 2009" section and reference the following assemblies:
using Castle.Components.Common.TemplateEngine.NVelocityTemplateEngine;
using Castle.Components.Common.TemplateEngine;
Then you can simply call:
using (var writer = new StringWriter())
{
_templateEngine.Process(data, string.Empty, writer, _templateContents);
return writer.ToString();
}
Where:
_templateEngine is your NVelocityTemplateEngine
data is your Dictionary of information (I'm using a Dictionary to enable me to access objects by a key ($objectKeyName) in my template.
_templateContents is the actual template string itself.
I hope this is of help to you!
Just to add, you'll want to put that into a static method returning a string of course!
Had this issue recently - NVelocity needs to be initialised with the location of the template files. In this case mergeValues is an anonymous type so in my template I can just refer to $Values.SomeItem:
private string Merge(Object mergeValues)
{
var velocity = new VelocityEngine();
var props = new ExtendedProperties();
props.AddProperty("file.resource.loader.path", #"D:\Path\To\Templates");
velocity.Init(props);
var template = velocity.GetTemplate("MailTemplate.vm");
var context = new VelocityContext();
context.Put("Values", mergeValues);
using (var writer = new StringWriter())
{
template.Merge(context, writer);
return writer.ToString();
}
}
Try setting the file.resource.loader.path
http://weblogs.asp.net/george_v_reilly/archive/2007/03/06/img-srchttpwwwcodegenerationnetlogosnveloc.aspx
Okay - So I'm managed to get something working but it is a bit of a hack and isn't anywhere near a solution that I want, but it got something working.
Basically, I manually load in the template into a string then pass that string to the velocityEngine.Evaluate() method which writes the result into the the given StringWriter. The side effect of this is that the #parse instructions in the template don't work because it still cannot find the files.
using (StringWriter writer = new StringWriter())
{
velocityEngine.Evaluate(context, writer, templateName, template);
return writer.ToString();
}
In the code above templateName is irrelevant as it isn't used. template is the string that contains the entire template that has been pre-loaded from disk.
I'd still appreciate any better solutions as I really don't like this.
The tests are the ultimate authority:
http://fisheye2.atlassian.com/browse/castleproject/NVelocity/trunk/src/NVelocity.Tests/Test/ParserTest.cs?r=6005#l122
Or you could use the TemplateEngine component which is a thin wrapper around NVelocity that makes things easier.
I need to create an xml file here
bool result= false;
How to achieve this in ASP.NET with C# syntax. result is value that I need to add in the XML file.
I need to create an XML file under a folder with contents like this
<?xml version="1.0" encoding="utf-8" ?>
<user>
<Authenticated>yes</Authenticated>
</user>
thank you
XElement xml = new XElement("user",
new XElement("Authenticated","Yes"))
);
xml.Save(savePath);
It works for .net 3 and above, but
You can use XmlDocument for later versions
XmlDocument xmlDoc = new XmlDocument();
// Write down the XML declaration
XmlDeclaration xmlDeclaration = xmlDoc.CreateXmlDeclaration("1.0","utf-8",null);
// Create the root element
XmlElement rootNode = xmlDoc.CreateElement("user");
xmlDoc.InsertBefore(xmlDeclaration, xmlDoc.DocumentElement);
xmlDoc.AppendChild(rootNode);
// Create the required nodes
XmlElement mainNode = xmlDoc.CreateElement("Authenticated");
XmlText yesText= xmlDoc.CreateTextNode("Yes");
mainNode.AppendChild(yesText);
rootNode.AppendChild(mainNode);
xmlDoc.Save(savePath);
You can use XmlWriter too as suggests #marc_s or at least you can store xml to the file like sting
using(StreamWriter sw = new StreamWriter(savePath))
{
sw.Write(string.Format("<?xml version=\"1.0\" encoding=\"utf-8\" ?>
<user><Authenticated>{0}</Authenticated></user>","Yes"));
}
How about this:
XmlTextWriter xtw = new XmlTextWriter(#"yourfilename.xml", Encoding.UTF8);
xtw.WriteProcessingInstruction("xml", "version=\"1.0\" encoding=\"utf-8\"");
xtw.WriteStartElement("user");
xtw.WriteStartElement("Authenticated");
xtw.WriteValue(result);
xtw.WriteEndElement(); // Authenticated
xtw.WriteEndElement(); // user
xtw.Flush();
xtw.Close();
Or if you prefer to build up your XML file in memory, you can also use the XmlDocument class and its methods:
// Create XmlDocument and add processing instruction
XmlDocument xdoc = new XmlDocument();
xdoc.AppendChild(xdoc.CreateProcessingInstruction("xml", "version=\"1.0\" encoding=\"utf-8\""));
// generate <user> element
XmlElement userElement = xdoc.CreateElement("user");
// create <Authenticated> subelement and set it's InnerText to the result value
XmlElement authElement = xdoc.CreateElement("Authenticated");
authElement.InnerText = result.ToString();
// add the <Authenticated> node as a child to the <user> node
userElement.AppendChild(authElement);
// add the <user> node to the XmlDocument
xdoc.AppendChild(userElement);
// save to file
xdoc.Save(#"C:\yourtargetfile.xml");
Should work on any version of the .NET framework, if you have a using System.Xml; clause at the top of your file.
Marc
If you want to generate the XML and then give the user a choice to save the XML in their workstation, check the post below. It explains that process in detail.
Generating XML in Memory Stream and download