Read xml file containing multiple tags with same attribute name and replace the value based on user's input

Question

Below is my sample XML file stored in the server ;

<exam>
  <name>Maths</name>
  <percentage>100</percentage>
</exam>
<exam>
  <name>Physics</name>
  <percentage>70</percentage>
</exam>
<exam>
  <name>Chemistry</name>
  <percentage>70</percentage>
</exam>

I have another table as mentioned below

Name of Exam                            Percentage
Maths                                       50
Physics                                     60
Chemistry                                   70

What I need here is that I need to read this XML File and replace the percentage value in the XML file based on the table that I have. I have more than 75 tags for exam

I have used the below logic of hardcoding everything but I am not sure if my logic would be good

    public static void Changepercentage()
    {
        try{

            string xmlpercentage= Loaddefault.xmlpercentage;

            string f = xml
            List<string> lines = new List<string>();

            // 2
            // Use using StreamReader for disposing.
            using (StreamReader r = new StreamReader(f, System.Text.Encoding.Default))
            {
                // 3
                // Use while != null pattern for loop
                string line;

                while ((line = r.ReadLine()) != null)
                {
                    if (System.Text.RegularExpressions.Regex.IsMatch(line, "<exam>Maths</exam>"))
                    {
                        lines.Add(@"" + line + "");
                        line = "<percentage>50</percentage>";
                    }                       
                }
            }


            System.IO.File.WriteAllLines(xmlpercentage, lines.ToArray());

            Logger.Instance.InfoLog("Successfully updated the percentage.xml file");
        }
        catch (Exception ex)
        {

            Logger.Instance.ErrorLog("Problem in updating the percentage.xml file :"+ ex.Message);
            throw new Exception("Problem in updating the percentage.xml file");
        }

    }

Okay, so how far have you got? I would suggest using LINQ to XML for all of this - it's a very pleasant XML API. What is the format of your table? Is it a text file, or in a database, or something else? Do you already have code to work with that? Basically, you've asked a fairly broad question at the moment with no indication of what you've tried or what specific problem you've got. — Jon Skeet
– Jon Skeet, Commented May 12, 2016 at 6:28
I have code to read the data from that table. I need logic only to read the XML file and replace the percentage values. — stangada
– stangada, Commented May 12, 2016 at 6:31
I have updated what I have got but I am not sure if that is the right way to proceed. — stangada
– stangada, Commented May 12, 2016 at 6:37
No, it absolutely isn't. You're trying to manipulate XML, so use an XML API as I said in the first comment. — Jon Skeet
– Jon Skeet, Commented May 12, 2016 at 6:38
This answer link will be also useful.. stackoverflow.com/a/1487764/1660178 — sangram parmar
– sangram parmar, Commented May 12, 2016 at 6:44

sangram parmar · Accepted Answer · 2016-05-12 06:38:55Z

1

You can use this documentation

//Make sure that the project references the System.Xml namespace.
//Use the Imports statement on the Xml namespace

using System.Xml;

//Create a new XmlDocument class, and use the Load method to load it.

XmlDocument myXmlDocument = new XmlDocument();
myXmlDocument.Load ("test.xml");

//Iterate through the children of the document element, and find all the "percentage" nodes. and update it.

foreach(XmlNode node1 in node.ChildNodes)
   foreach (XmlNode node2 in node1.ChildNodes)
      if (node2.Name == "percentage")
         {
            Decimal percentage = 60;//your new percentage
            node2.InnerText = percentage;
          }

//Use the Save method of the XmlDocument class to save the altered XML to a new file that is named test1.xml.         

myXmlDocument.Save("test1.xml");

edited May 12, 2016 at 6:38

answered May 12, 2016 at 6:38

sangram parmar

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4 Comments

Jon Skeet Over a year ago

This is much more convoluted than the equivalent LINQ to XML would be.

sangram parmar Over a year ago

I think it is much basic implementation. And that article has been archived...but it will be works

Jon Skeet Over a year ago

Yes, it will work - but why provide a complex approach when there are simpler ones with more modern APIs? Would you give an answer using ArrayList rather than List<T>?

sangram parmar Over a year ago

@JonSkeet Yes you are absolutely right...I have no argument to you...I am fan of you.You are my role model for the programming.

Chrisi · Accepted Answer · 2016-05-12 06:39:13Z

0

Iterate over all <exam> nodes of your XML, read the child node <name>. With the InnerText of name query the data base and put the data base result into the <percentage> node.

Something like this should do:

var doc = XDocument.Parse(yourXml);
foreach(XElement exam in doc.Descendants("exam"))
{
    var examName = exam.Descendants("name").First().Value;
    var newPercentage = GetPercentage(examName);
    exam.Descendants("percentage").First().Value = newPercentage;
}

answered May 12, 2016 at 6:39

Chrisi

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1 Comment

Jon Skeet Over a year ago

Note that a simpler way of getting the first child element with a particular name is to just use Element("foo"). I'd also use the explicit conversions, e.g. var examName = (string) exam.Element("name");

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