Edit and Delete data from XML file using ASP.net and VB.net (or C#)

Question

In my web application, i have an XML file called "answers.xml"

it store the user entries in XML

<?xml version=""1.0""?> <Answers>  
<AnswerSet> <Answer questionId=""MRN"">4444</Answer> 
<Answer questionId=""FName"">test</Answer> 
<Answer questionId=""LName"">patient</Answer> 
<Answer questionId=""AddressPt"">blah blah</Answer> 
<Answer questionId=""Governorate"">xxxx</Answer> 
<Answer questionId=""InitialCSF"">Negative</Answer> 
<Answer questionId=""Diagnosis""></Answer> 
<Answer questionId=""Description""> </Answer>   
</AnswerSet>   
<AnswerSet> 
<Answer questionId=""MRN"">1</Answer> 
<Answer questionId=""FName"">1</Answer> 
<Answer questionId=""LName"">1</Answer> 
<Answer questionId=""AddressPt"">1</Answer> 
<Answer questionId=""InitialCSF"">Positive</Answer> 
<Answer questionId=""Diagnosis"">dx</Answer> 
<Answer questionId=""Description""> </Answer>   
</AnswerSet>  </Answers>

i can add data to the XML file using a DLL file i downloaded from the internet. i need a way to change the data (edit / delete) in the xml file using ASP.net / VB.net or C#

Saeed Amiri · Accepted Answer · 2011-11-09 21:36:55Z

3

I prefer to use XDocument, because simply you can search it and change the elements or attributes:

XDocument doc1 = XDocument.Parse("<AnswerSet> <Answer questionId=\"10\" FName=\"test\"> </Answer></AnswerSet> ");
// or if you have related file simply use XDocument doc1 = XDocument.Load(fileFullName);
var element =
      doc1.Descendants("AnswerSet").Elements("Answer")
      .Where(x => x.Attribute("FName") != null 
            && x.Attribute("FName").Value == "test").SingleOrDefault();
if (element != null)
{
   var attr = element.Attribute("FName");
   attr.Value = "Changed";
}

doc1.Save(filePath);

Edit: Descendants("AnswerSet") finds AnswerSet elements, Elements("Answer") finds Answer Elements,

Where(x => x.Attribute("FName") != null 
            && x.Attribute("FName").Value == "test").SingleOrDefault();

finds element which contains attribute FName and attribute value equals to test, SingleOrDefault in the last, says you should have just one such an element, Also you can change it (just call ToList()) to find all related elements, and finally in if I'll change the value of element, Also at the end we save it again with changed values.

This language (linq2xml) is too easy and functions like Descendant and Elements are most use full functions in it, so there is no need to have special knowledge you can simply come up to many problems by knowing this functions.

edited Nov 9, 2011 at 21:36

answered Nov 9, 2011 at 21:29

Saeed Amiri

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5 Comments

Saeed Amiri Over a year ago

I didn't mention Remove cause it's very simple and as you can see it's documented by MSDN.

Mohamed Kamal Over a year ago

thanks @Saeed Amiri vote up. but u suggested a solution that works with fixed field names. normal user cant do anything if he needs to add a new field, right? i was thinking of a solution that load all fields into a gridview, then edit and update. whenever we add a new field, it populates in the gridview without code modification.

Saeed Amiri Over a year ago

@mokokamello editing element in XML is different thing than editing grideview, in fact you can load your xml in gridview, by simply getting Filed values into list, but this code is different from updating or editing, because your classes should be separated from each other as many as possible, specially your way of saving or business should be hide from UI implementation, If next day you want move it to silver light, again you should code, this known as Separation Of Concern rule. Also this can be dynamic and affect on many fields, but I prevent from wrote it cause of confusion.

Mohamed Kamal Over a year ago

thanks @Saeed Amiri, i understand from u it is very difficult to edit in XML file, or is it doable. please help me :)

Saeed Amiri Over a year ago

@mokokamello it's not difficult first read something about linq (for e.g google 101 linq sample, and test them) then you simply can handle all of your requirements, and then if you have a problem, we are here to help you, I wrote this answer to introduce you, DOM and SAX are other options for working with xml but they are old and is better to use XDocument.

Remy · Accepted Answer · 2011-11-09 21:22:22Z

2

You can just use the XmlDocument class that comes with .Net. No need to download something. Or do I miss something?

First thing I found, it's for VB, but the concept stays the same for c#.
http://support.microsoft.com/kb/317662

You can just load any xml file and then use XPath to access any node and change it.

edited Nov 9, 2011 at 21:22

answered Nov 9, 2011 at 21:14

Remy

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1 Comment

Mohamed Kamal Over a year ago

i never used xml for datastorage before, so please be patient with me and tell me more details

Lloyd · Accepted Answer · 2011-11-08 22:57:21Z

1

Have you looked at the XmlDataSource Control.

answered Nov 8, 2011 at 22:57

Lloyd

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