Im trying to open and edit XML file inside Silverlight element, but I can't edit it.
My XML file (Customers.xml) looks like this:
<?xml version="1.0"?>
<customers>
<customer>Joe</customer>
<customer>Barrel</customer>
</customers>
And my C# logic:
[...]
XDocument xdoc = XDocument.Load("Customers.xml");
xdoc.Root.Add(new XElement("customer", "Stephano")); //here I wish it to add Stephano as a customer.
using (var file = IsolatedStorageFile.GetUserStoreForApplication())
{
using (var stream = file.OpenFile("Customers.xml", FileMode.Create))
{
xdoc.Save(stream); //and here I wish it to save it to the file
}
}
PopulateCustomersList();
/\ here is a function that is used to display the content of XML file, it goes:
private void PopulateCustomersList()
{
XmlReaderSettings settings = new XmlReaderSettings();
settings.XmlResolver = new XmlXapResolver();
XmlReader reader = XmlReader.Create("Customers.xml");
reader.MoveToContent();
while (reader.Read())
{
if (reader.NodeType == XmlNodeType.Element && reader.Name == "customer")
{
//OutputTextBlock.Text = reader.GetAttribute("first");
customersList.Items.Add(new ListBoxItem()
{
Content = reader.ReadInnerXml()
});
}
if (reader.NodeType == XmlNodeType.EndElement && reader.Name == "customers")
{
break;
}
}
reader.Close();
}
In my xaml file I have
<ListBox x:Name="customersList" />
so it gets displayed, but the problem is that only Joe and Barrel gets to be displayed and where is Stephano?
I got this code from various tutorials and forums, I don't quite understand it, I know it may be strange way to do that, but I just can't find out how to do that and I'm trying all sort of things. The funniest thing is that I found on many forums a way to save the file, which looks like this:
xdoc.Save("Customers.xml"); but my Visual Studio says that the arguments are wrong, because it is a string. How am I supposed to tell him that its a file?
Okay:
.Save() saves the current XDocument, I.E it's going to save the XML file you loaded up here
XDocument xdoc = XDocument.Load("Customers.xml");
So it should be something like (this is coded without any knowledge more than you provided)
XDocument xdoc = XDocument.Load("Customers.xml");
xdoc.Root.Add(new XElement("customer", "Stephano"));
xdoc.Save();
PopulateCustomersList(xdoc);
private void PopulateCustomersList(XDocument xdoc)
{
foreach(XElement in element xdoc.Root.Elements("customer"))
{
customersList.Items.Add(new ListBoxItem()
{
Content = (string)element;
}
}
}
Related
I am using XmlReader.ReadInnerXml() to load part of an XML file and save it as an XmlDocument. I ran into OutOfMemoryException when the innerXml part was over 2 GB (an estimate). What is the best way to handle this error? Is there a better way to create a large xml from XmlReader? Can I save the content without loading into memory?
using (XmlReader xmlRdr = XmlReader.Create(file))
{
xmlRdr.MoveToContent();
while (xmlRdr.Read())
{
//when read to XmlNodeType.Element and xmlRdr.Name meets certain criteria
XmlDocument xmlDoc = new XmlDocument();
xmlDoc.PreserveWhitespace = true;
try
{
xmlDoc.LoadXml(xmlRdr.ReadInnerXml());
//get a few data from within the innerXml and eventually use XmlWritter to save the file
}
catch(Exception e)
{
string content = $"{e.GetType()} {e.Message} {NewLine} {objId}";
//send content to log file and email
}
}
}
As said in one of the comments maybe try using StreamReader and StreamWriter
This tutorial might help
I have a very large xml-file (let's say it has about 300000 elements). In my part of the application I only have to know if the name of the root-element is ApplicationLog and if there is an attribute called LogId in the root-element.
To read the XML I use:
XDocument document;
using (StreamReader streamReader = new StreamReader(filePath, true))
{
document = XDocument.Load(streamReader);
}
and to get the information I need:
try
{
if (document.Root != null)
{
if (string.Equals(document.Root.Name.LocalName, "ApplicationLog", StringComparison.InvariantCultureIgnoreCase) &&
document.Root.HasAttributes && (from o in document.Root.Attributes() where string.Equals(o.Name.LocalName, "LogId", StringComparison.InvariantCultureIgnoreCase) select o).Any())
{
isRelevantFile = true;
}
}
}
catch (Exception e)
{
}
This just works fine.
The problem is that the XDocument.Load takes about 15 seconds to load a XML-File which is about 20MB.
I also tried it with the XmlDocument, but there I have the same problem.
My first idea for a solution was to read the file as text and parse the first lines for the searched element/attribute. But this seems to be not so professional to me.
Does anybody know a better way to achieve this?
Use the XmlReader API with
using (XmlReader xr = XmlReader.Create(filePath))
{
xr.MoveToContent();
if (xr.LocalName == "ApplicationLog" ...)
}
You can try the solution provided here or use/develop a SAX reader such as this one. You can find more information on SAX here.
This question already has answers here:
XDocument Get Part of XML File
(3 answers)
Closed 8 years ago.
I did write this code to read a url of xml file:
XDocument feedXml = XDocument.Load("url address of xml file here");
var feeds = from feed in feedXml.Descendants("List")
select new Event {
Id = Int32.Parse(feed.Element("ID").Value),
Name = feed.Element("Name").Value,
City = feed.Element("City").Value
};
return feeds;
My problem is that the file is too large (about 40MB) and take too much time to load.
So I am using XmlReader to read xml file but this was not applicable too because I don't know how to load every (for example 10) records in every page on demand and I should read the whole file every time and skip other records to reach appropriate elements, shouldn't I?
string XmlFileUrl = #"url address of xml file here";
using (XmlReader reader = new XmlTextReader(XmlFileUrl))
{
bool openItem = false;
Event item = new Event();
while (reader.Read())
{
if (reader.NodeType == XmlNodeType.Element)
{
if (reader.Name == "List")
{
item = new Event();
openItem = true;
}
else if (reader.Name == "Name" && openItem)
item.Name = reader.ReadElementContentAsString();
...
}
else if (reader.NodeType == XmlNodeType.EndElement && reader.Name == "List" && openItem)
{
openItem = false;
feeds.Add(item);
}
}
}
Is there any way to use Jquery ajax or convert the xml file to json with paging to load just needed data on every page, or any suggestion?
I think this is not so easy to achieve with a XML structure and maybe in this case is XDocument.Load not the appropriate method, because AFAIK it always loads the whole document immediately. You can try the overload with the Stream parameter, instead of URL, and try loading only a part of the the file over the net. Probably you need to write your own loader (that gets only a portion of the file, maybe XmlDocument?) and parse the incomplete structure by yourself.
If you can call portions of the XML file controlled by the URI (for example: http://domain/entries?page=10&take=20 and this call returns a valid XML), then an option would be to use this URL instead of the link to the whole file, something like:
var pagedUri = #"http://domain/entries?page=10&take=20";
XDocument feedXml = XDocument.Load(pagedUri);
var feeds = from feed in feedXml.Descendants("List")
select new Event {
Id = Int32.Parse(feed.Element("ID").Value),
Name = feed.Element("Name").Value,
City = feed.Element("City").Value
};
return feeds;
Have a look at this SO post where a similar problem is addressed.
I am building a Windows 8 app, and I need to extract the whole XML node and its children as string from a large xml document, and the method that does that so far looks like this:
public string GetNodeContent(string path)
{
XmlReaderSettings settings = new XmlReaderSettings();
settings.IgnoreWhitespace = true;
settings.ConformanceLevel = ConformanceLevel.Auto;
settings.IgnoreComments = true;
using (XmlReader reader = XmlReader.Create("something.xml", settings))
{
reader.MoveToContent();
reader.Read();
XmlDocument doc = new XmlDocument();
doc.LoadXml(reader.ReadOuterXml());
IXmlNode node = doc.SelectSingleNode(path);
return node.InnerText;
}
}
When I pass any form of xpath, node gets the value of null. I'm using the reader to get the first child of root node, and then use XMLDocument to create one from that xml. Since it's Windows 8, apparently, I can't use XPathSelectElements method and this is the only way I can't think of. Is there a way to do it using this, or any other logic?
Thank you in advance for your answers.
[UPDATE]
Let's say XML has this general form:
<nodeone attributes...>
<nodetwo attributes...>
<nodethree attributes... />
<nodethree attributes... />
<nodethree attributes... />
</nodetwo>
</nodeone >
I expect to get as a result nodetwo and all of its children in the form of xml string when i pass "/nodeone/nodetwo" or "//nodetwo"
I've come up with this solution, the whole approach was wrong to start with. The problematic part was the fact that this code
reader.MoveToContent();
reader.Read();
ignores the namespace by itself, because it skips the root tag. This is the new, working code:
public static async Task<string> ReadFileTest(string xpath)
{
StorageFolder folder = await Package.Current.InstalledLocation.GetFolderAsync("NameOfFolderWithXML");
StorageFile xmlFile = await folder.GetFileAsync("filename.xml");
XmlDocument xmldoc = await XmlDocument.LoadFromFileAsync(xmlFile);
var nodes = doc.SelectNodes(xpath);
XmlElement element = (XmlElement)nodes[0];
return element.GetXml();
}
How do i know if my XML file has data besides the name space info:
Some of the files contain this:
<?xml version="1.0" encoding="UTF-8"?>
And if i encounter such a file, i want to place the file in an error directory
You could use the XmlReader to avoid the overhead of XmlDocument. In your case, you will receive an exception because the root element is missing.
string xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>";
using (StringReader strReader = new StringReader(xml))
{
//You can replace the StringReader object with the path of your xml file.
//In that case, do not forget to remove the "using" lines above.
using (XmlReader reader = XmlReader.Create(strReader))
{
try
{
while (reader.Read())
{
}
}
catch (XmlException ex)
{
//Catch xml exception
//in your case: root element is missing
}
}
}
You can add a condition in the while(reader.Read()) loop after you checked the first nodes to avoid to read the entire xml file since you just want to check if the root element is missing.
I think the only way is to catch an exception when you try and load it, like this:
try
{
System.Xml.XmlDocument doc = new System.Xml.XmlDocument();
doc.Load(Server.MapPath("XMLFile.xml"));
}
catch (System.Xml.XmlException xmlEx)
{
if (xmlEx.Message.Contains("Root element is missing"))
{
// Xml file is empty
}
}
Yes, there is some overhead, but you should be performing sanity checks like this anyway. You should never trust input and the only way to reliably verify it is XML is to treat it like XML and see what .NET says about it!
XmlDocument xDoc = new XmlDocument();
if (xDoc.ChildNodes.Count == 0)
{ // xml document is empty }
if (xDoc.ChildNodes.Count == 1)
{ // in xml document is only declaration node. (if you are shure that declaration is allways at the begining }
if (xDoc.ChildNodes.Count > 1)
{ // there is declaration + n nodes (usually this count is 2; declaration + root node) }
Haven't tried this...but should work.
try
{
XmlDocument doc = new XmlDocument();
doc.Load("test.xml");
}
catch (XmlException exc)
{
//invalid file
}
EDIT: Based on feedback comments
For large XML documents see Thomas's answer. This approach can have performance issues.
But, if it is a valid xml and the program wants to process it then this approach seems better.
If you aren't worried about validity, just check to see if there is anything after the first ?>. I'm not entirely sure of the C# syntax (it's been too long since I used it), but read the file, look for the first instance of ?>, and see if there is anything after that index.
However, if you want to use the XML later or you want to process the XML later, you should consider PK's answer and load the XML into an XmlDocument object. But if you have large XML documents that you don't need to process, then a solution more like mine, reading the file as text, might have less overhead.
You could check if the xml document has a node (the root node) and check it that node has inner text or other children.
As long as you aren't concerned with the validity of the XML document, and only want to ensure that it has a tag other than the declaration, you could use simple text processing:
var regEx = new RegEx("<[A-Za-z]");
bool foundTags = false;
string curLine = "";
using (var reader = new StreamReader(fileName)) {
while (!reader.EndOfStream) {
curLine = reader.ReadLine();
if (regEx.Match(curLine)) {
foundTags = true;
break;
}
}
}
if (!foundTags) {
// file is bad, copy.
}
Keep in mind that there's a million other reasons that the file may be invalid, and the code above would validate a file consisting only of "<a". If your intent is to validate that the XML document is capable of being read, you should use the XmlDocument approach.