I'm developing a windows app using C#. I chose xml for data storage.
It is required to read xml file, make small changes, and then write it back to hard disk.
Now, what is the easiest way of doing this?
XLinq is much comfortable than the ordinary Xml, because is much more object oriented, supports linq, has lots of implicit casts and serializes to the standard ISO format.
The best way is to use XML Serialization where it loads the XML into a class (with various classes representing all the elements/attributes). You can then change the values in code and then serialize back to XML.
To create the classes, the best thing to do is to use xsd.exe which will generate the c# classes for you from an existing XML document.
I think the easiest way of doing it - it is using XmlDocument class:
var doc = new XmlDocument();
doc.Load("filename or stream or streamwriter or XmlReader");
//do something
doc.Save("filename or stream or streamwriter or XmlWriter");
I think I found the easiest way, check out this Project in Codeproject. It is easy to use as XML elements are accessed similarly to array elements using name strings as indexes.
Code sample to write bool property to XML:
Xmlconfig xcfg = new Xmlconfig("config.xml", true);
xcfg.Settings[this.Name]["AddDateStamp"]["bool"].boolValue = checkBoxAddStamp.Checked;
xcfg.Save("config.xml");
Sample to read the property:
Xmlconfig xcfg = new Xmlconfig("config.xml", true);
checkBoxAddStamp.Checked = xcfg.Settings[this.Name]["AddDateStamp"]["bool"].boolValue;
To write string use .Value, for int .intValue.
You can use LINQ to read XML Files as described here...
LINQ to read XML
Check out linq to XML
Related
I have been looking all over for the best way to update xml in a file. I have just switched over to using XmlReader (coming from the XDocument method) for speed (not having to read the entire file in memory).
My XmlReader method works perfect and when I need to read a value, it opens the xml, starts reading and ONLY reads up to the node needed, then closes everything. It's very fast and effective.
Now that I have that working I want to make a method that UPDATES xml that is already in place. I would like to keep to the same idea and ONLY read in memory what is needed. So the idea would be, read up until the node I'm changing then use the writer to UPDATE that value.
Everything I have seen has a XmlReader reading while using an XmlWriter writing everything. If I did that I would assume that I would have to let it run through the entire file just like the XDocument would do. As an example this answer.
Is it possible to maybe just use the reader and read up to the node I'm trying to edit then change the innerxml or something?
What's the fastest and most efficient method to update XML in a file?
I would like to only read into memory what I'm trying to edit, not
the whole file.
I would also like to account for nodes that do not
exist (that need to be added).
By design, XmlReader represents a "read-only forward-only" view of the document and cannot be used to update the content. Using the Load method of either XmlDocument, XDocument or XElement, will still cause the entire file to be read in to memory. (Under the hood, XDocument and XElement still use an XmlReader.) However, you can combine using a raw XmlReader and XElement together using the overloads of the Load method which take an XmlReader.
You don't describe your XML structure, but you would want to do something similar to this:
var reader = XmlReader.Create(#"file://c:\test.xml");
var document = XElement.Load(reader);
document.Add(new XElement("branch", "leaves"));
document.Save("Tree.xml");
To find a specific node (for example, with a specific attribute value), you'd want to do something similar to this:
var node = document.Descendants("branch")
.SingleOrDefault(e => (string)e.Attribute("name") == "foo");
I have an xml response string and I want to change a value inside and log it.
<xml>
<ns2:abcd>
<password>sample</password>
</ns2:abcd>
I want to change the password value into encrypted version.
I am have tried using XmlDocument.SelectSingleNode but was thinking is there any better way than this?
Btw you need ns2 namespace to be declared, otherwise your xml will not be valid. After adding namespace definition, you can parse and modify your xml with Linq to Xml:
XDocument xdoc = XDocument.Parse(xml);
var passwordElement = xdoc.XPathSelectElement("//password");
passwordElement.Value = Encrypt((string)passwordElement);
xdoc.Save(path_to_xml);
No - there is no better way than using proper XML classes.
XmlDocument or XDocument would be perfectly fine for this task. If you XML is very large you may want to look into streaming with XmlReader (unlikely necessary in your case).
You might also consider looking into xsd.exe. With xsd.exe, you can deserialize your xml into a type-safe object model. From there, it's easy to manipulate the data.
How to add a new node, update an existing node and remove an existing node of an xml document without loading the whole document in memory?
I'm having an xml document and treating it as the memory of my application so would need to be able to do hundreds of reads and writes quickly without loading the whole document.
its structure is like this:
<spiderMemory>
<profileSite profileId="" siteId="">
<links>
<link>
<originalUrl></originalUrl>
<isCrawled></isCrawled>
<isBroken></isBroken>
<isHtmlPage></isHtmlPage>
<firstAppearedLevel></firstAppearedLevel>
</link>
</links>
</profileSite>
</spiderMemory>
How would that be possible with XDocument?
Thanks
If you want to do hundreds of reads and writes quickly... you might be using the wrong technology. Have you tried using a plain old RDBMS?
If you still need the XML representation, then you can create an export methods to produce it from the database.
XML isn't really a good substitute for this kind of problem. Just saying.
Also... what is wrong with having the whole thing in memory? How big can it possibly get? Say 1GB? Suck it up. Say 1TB? Oops. But then XML is wrong, wrong, wrong anyway in that case ;) way too verbose!
You can use XmlReader, something like this :
FileStream stream = new FileStream("test.xml", FileMode.Open);
XmlReader reader = new XmlTextReader(stream);
while(reader.Read())
{
Console.WriteLine(reader.Value);
}
here is an more elaborate example http://msdn.microsoft.com/en-us/library/cc189056%28v=vs.95%29.aspx
As Daren Thomas said, the proper solution is to use RDBMS instead of XML for your needs. I have a partial solution using XML and Java. Stax parser does not parse the whole document in memory and is a lot faster than DOM (still XML parsing will always be slow). A 'pull parser' (eg Stax) allows u to control what gets parsed. A less cleaner way is to throw an exception in SAX parser when you get the element(s) needed.
To modify, the simplest (but slow) way is to use XPath. Another (untested) option is to treat XML file as text and then 'Search and replace' stuff. Here you can use all kinds of text search optimization.
I have a string containing fully formatted XML data, created using a Perl script.
I now want to convert this string into an actual XML file in C#. Is there anyway to do this?
Thanks,
You can load a string into an in-memory representation, for example, using the LINQ to SQL XDocument type. Loading string can be done using Parse method and saving the document to a file is done using the Save method:
open System.Xml.Linq;
XDocument doc = XDocument.Parse(xmlContent);
doc.Save(fileName);
The question is why would you do that, if you already have correctly formatted XML document?
A good reasons that I can think of are:
To verify that the content is really valid XML
To generate XML with nice indentation and line breaks
If that's not what you need, then you should just write the data to a file (as others suggest).
Could be as simple as
File.WriteAllText(#"C:\Test.xml", "your-xml-string");
or
File.WriteAllText(#"C:\Test.xml", "your-xml-string", Encoding.UTF8);
XmlDocument doc = new XmlDocument();
doc.Load(... your string ...);
doc.Save(... your destination path...);
see also
http://msdn.microsoft.com/fr-fr/library/d5awd922%28v=VS.80%29.aspx
I'm working on a project for school that involves a heavy amount of XML Parsing. I'm coding in C#, but I have yet to find a "suitable" method of parsing this XML out. There's several different ways I've looked at, but haven't gotten it right yet; so I have come to you. Ideally, I'm looking for something kind of similar to Beautiful Soup in Python (sort of).
I was wondering if there was any way to convert XML like this:
<config>
<bgimg>C:\\background.png</bgimg>
<nodelist>
<node>
<oid>012345</oid>
<image>C:\\image.png</image>
<label>EHRV</label>
<tooltip>
<header>EHR Viewer</header>
<body>Version 1.0</body>
<icon>C:\\ico\ehrv.png</icon>
</tooltip>
<msgSource>8181:iqLog</msgSource>
</nodes>
</nodeList>
<config>
Into an Array/Hastable/Dictionary/Other like this:
Array
(
["config"] => array
(
["bgimg"] => "C:\\background.png"
["nodelist"] => array
(
["node"] => array
(
["oid"] => "012345"
["image"] => "C:\\image.png"
["label"] => "Version 1.0"
["tooltip"] => array
(
["header"] => "EHR Viewer"
["body"] => "Version 1.0"
["icon"] => "C:\\ico\ehrv.png"
)
["msgSource"] => "8181:iqLog"
)
)
)
)
Even just giving me a decent resource to look through would be really helpful. Thanks a ton.
I would look into Linq to Xml. This gives you an object structure similar to the Xml file that is fairly easy to traverse.
XmlDocument + XPath is pretty much all you ever need in .NET to parse XML.
There must be 1/2 dozen different ways to do this in C#. My favorite uses the System.Xml namespace, particularly System.Xml.Serialization.
You use a command line tool called xsd.exe to turn an xml sample into an xsd schema file (tip: make sure your nodelist has more than one node in the sample), and then use it again on the schema to turn that into a C# class file you can load into your project and easily use with the System.Xml.Serialization.XmlSerializer class.
There's no shame in using an old-fashioned XmlDocument:
var xml = "<config>hello world</config>";
var doc = new System.Xml.XmlDocument();
doc.LoadXml(xml);
var nodes = doc.SelectNodes("/config");
You should defiantly use LINQ to XML, A.K.A. XLINQ. There is a nice tool called LINQPad that you should check out. It has nice features, from a comprehensive examples library to allowing you to directly query an SQL database via Linq to SQL. Best of all, it lets you test your queries before putting them into code.
The best approach will be dictated by what you actually want to do with the data once you've parsed it out.
If you want to pass it around in a structured-but-not-tied-to-XML fashion, XML Serialization is probably your best bet. This will also get you closest to what you've described, though you'll be dealing with an object graph rather than nested maps.
If you are just looking for a convenient format to query for specific bits of data, your best option would be LINQ to Xml. Alternatively, you could use the more traditional classes in the System.Xml namespace (starting with XmlDocument) and query using XPath.
You could also use any of these techniques (or an XmlTextReader) as building blocks to create the datastructure you've described but, barring some special need, I don't think it'll give you any more versatility than what the other approaches will.
You can also use serialization to convert the XML text back into a strongly typed class instance.
I personally like to map XML elements to classes and viceversa using System.Xml.Serialization.XmlSerializer class.
http://msdn.microsoft.com/es-es/library/system.xml.serialization.xmlserializer(VS.80).aspx
I personally use XPathDocument, XPathNavigator and XPathNodeIterator e.g.
XPathDocument xDoc = new XPathDocument(CHOOSE SOURCE!);
XPathNavigator xNav = xDoc.CreateNavigator();
XPathNodeIterator iterator = xNav.Select("nodes/node[#SomePredicate = 'SomeValue']");
while (iterator.MoveNext())
{
string val = iterator.Current.SelectSingleNode("nodeWithValue");
// etc etc
}
Yeah, i agree..
The linq-way is very nice.
And i especially like the way you write XML using it.
It is much more simple using the "objects in objects"-way.