How to get the desired substring from a string(xml) in an efficient way?

Question

I have C# application. Below is my string

<subscription_add_ons type="array">
    <subscription_add_on>
        <add_on_type>fixed</add_on_type>
        <add_on_code>bike-o-vision</add_on_code>
        <unit_amount_in_cents type="integer">2000</unit_amount_in_cents>
        <quantity type="integer">1</quantity>
        <revenue_schedule_type>evenly</revenue_schedule_type>
    </subscription_add_on>
    <subscription_add_on>
        <add_on_type>fixed</add_on_type>
        <add_on_code>boxx</add_on_code>
        <unit_amount_in_cents type="integer">1499</unit_amount_in_cents>
        <quantity type="integer">1</quantity>
        <revenue_schedule_type>evenly</revenue_schedule_type>
    </subscription_add_on>
    <subscription_add_on>
        <add_on_type>fixed</add_on_type>
        <add_on_code>fitfusion-strala</add_on_code>
        <unit_amount_in_cents type="integer">500</unit_amount_in_cents>
        <quantity type="integer">1</quantity>
        <revenue_schedule_type>evenly</revenue_schedule_type>
    </subscription_add_on>
</subscription_add_ons>

What I need is a substring from the above xml string as below.

<subscription_add_ons type="array">
    <subscription_add_on>
        <add_on_code>bike-o-vision</add_on_code>
        <quantity type="integer">1</quantity>
    </subscription_add_on>
    <subscription_add_on>
        <add_on_code>boxx</add_on_code>
        <quantity type="integer">1</quantity>
    </subscription_add_on>
    <subscription_add_on>
        <add_on_code>fitfusion-strala</add_on_code>
        <quantity type="integer">1</quantity>
    </subscription_add_on>
</subscription_add_ons>

I tried to get it as below.

var xml = _xml.GetXmlNodes(xmlString);
StringBuilder sb = new StringBuilder();
sb.Append("<subscription>");
foreach (XmlNode node in xml)
{
  var sIndex = node.OuterXml.IndexOf("<add_on_code>");
  var eIndex = node.OuterXml.IndexOf("</add_on_code>");
  var subs = "<subscription_add_on>" + node.OuterXml.Substring(sIndex, (eIndex - sIndex)) + "<quantity>1</quantity>" + " </subscription_add_on>";
            sb.Append(subs);
        }
 sb.Append("</subscription");

The above snippet always fetches the first substring & to me it looks very inefficient.

How can I get the desired substring from a string(xml) in an efficient way?

Thanks!

Instead of handling this as a string, use an XML parser https://stackoverflow.com/questions/5604330/xml-parsing-read-a-simple-xml-file-and-retrieve-values — Jasen, Mar 26 '19 at 17:50
What does `efficient way` mean? Readable? Maintainable? Performant? Extensible? Some of these don't mix well. — Erik Philips, Mar 31 '19 at 20:58

Magnetron · Accepted Answer · 2019-03-26T18:14:58.237

1

Just parse the xml and remove the undesired elements:

XDocument doc = XDocument.Load("fileName.xml");
//or
//XDocument doc = XDocument.Parse(textString);
foreach(var removeNode in new string[]{"add_on_type", "unit_amount_in_cents","revenue_schedule_type"})
{
    doc.Root.Descendants(removeNode).Remove();
}
string result = doc.ToString();

Edit: To add more elements, do this way:

doc.Root.Add(
    new XElement(
        "subscription_add_on", 
        new XElement("add_on_code","add_on_code_value"),
        new XElement("quantity",
            new XAttribute("type","integer"),
            1
        )
    )
);

edited Mar 26 '19 at 18:14

answered Mar 26 '19 at 17:51

Magnetron

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Many Thanks! One more thing to check if I want to add one more `` in the trimmed version. how can it be achived. – Kgn-web Mar 26 '19 at 18:09
@Kgn-web just edited the answer to add one more element – Magnetron Mar 26 '19 at 18:15
Thanks! but when doing so it add the new XELement as ` test 1` – Kgn-web Mar 27 '19 at 06:47
@Kgn-web it was not what you wanted? You can tweak the code according to your needs – Magnetron Mar 27 '19 at 11:01

How to get the desired substring from a string(xml) in an efficient way?

1 Answers1