How can I get the regex to work?

Question

I want to use a regex to find the parent node of the 16 digit number and return that whole section, but can't figure out how, so given:

<Details>
<CreditCard cardnum="1234567890123456" ccv="123" exp="0212" cardType="1" name="joe" />
</Details>

I want to return:

<CreditCard cardnum="1234567890123456" ccv="123" exp="0212" cardType="1" name="joe" />

I then am going to use parse the xml and get every attribute that is a number and remove it.

I tried .*(\\d{13,16}).* , but this gets every character.

Once, I do:

XElement element = XElement.Parse(xml); // XDocument.Load(xmlFile).Root

IEnumerable<XElement> elementsWithPossibleCCNumbers = 
        element.Descendants()
               .Where(d => d.Attributes()
                            .Where(a => a.Value.Length == 16)
                            .Count() == 1); 

I can't figure out how to loop through each attribute in elementsWithPossibleCCNumbers, for example:

foreach(var x in elementsWithPossibleCCNumbers)
{
//If attribute is number, replace value with empty string
}

Note: I removed the int.TryParse for now.

I decided to do this:

IEnumerable<XElement> elementsWithPossibleCCNumbers = 
        element.Descendants()
               .Where(d => d.Attributes()
                            .Where(a => a.Value.Length >= 13 && a.Value.Length <= 16)
                            .Count() == 1).Select(x=>x);


foreach(var x in elementsWithPossibleCCNumbers)
{
   foreach(var a in x.Attributes())
   {

   xml = xml.Replace(a.Value, new String('*',12));
   }
}

However, if I have a second element with an attribute of 16 digits, it only replaces part of the attributes value.

Answer 1

I wrote up another method to try out. The regex now only verifies the attribute value and not the XML itself. I have no idea what you're looking to return out from this method but this will at least get you started on not using Regex for XML.

[Test]
public void X()
{
    const string xml = "<Details><CreditCard cardnum=\"1234567890123456\" ccv=\"123\" exp=\"0212\" cardType=\"1\" name=\"joe\" /><donotfind>333</donotfind></Details>";

    var doc = new XmlDocument();
    doc.LoadXml(xml);

    Console.WriteLine(doc.Name);;

    foreach(XmlNode x in doc.ChildNodes)
    {
        ExploreNode(x);
    }
}

void ExploreNode(XmlNode node)
{
    Console.WriteLine(node.Name);

    if (node.Attributes != null)
    {
        foreach (XmlAttribute attr in node.Attributes)
        {
            Console.WriteLine("\t{0} -> {1}", attr.Name, attr.Value);

            if (attr.Value.Length == 16 && Regex.IsMatch(attr.Value, @"\d{16}"))
            {
                Console.WriteLine("\t\tCredit Card # found!");
            }
        }
    }

    foreach (XmlNode child in node.ChildNodes)
    {
        ExploreNode(child);
    }
}

Answer 2

Since your XML can vary a great deal, I would do something like the following.

Assuming XML like:

<Details> 
<CreditCard cardnum="1234567890123456" 
            ccv="123" 
            exp="0212" 
            cardType="1" 
            name="joe" /> 
</Details> 

Agnostic-ish code:

XElement element = XElement.Parse(xml); // XDocument.Load(xmlFile).Root
int ccNumber;

IEnumerable<XElement> elementsWithPossibleCCNumbers = 
        element.Descendants()
               .Where(d => d.Attributes()
                            .Where(a => a.Value.Length == 16)
                            .Where(a => int.TryParse(a.Value, out ccNumber))
                            .FirstOrDefault() != null);

// Do not use ccNumber 
// Use elementsWithPossibleCCNumbers

This could be extended to include a number of attributes...

IEnumerable<XElement> elementsWithPossibleCCNumbers =
        element.Descendants()
               .Where(d => d.Attributes()
                            .Where(a => a.Value.Length == 16)
                            .Where(a => int.TryParse(a.Value, out ccNumber))
                            .FirstOrDefault() != null
                           && d.Attributes().Count() == 5);

There are a multitude of possibilities that don't include using Regex nor hard coding XML element names. I tend to use Regex as a last resort, especially if there is something better that can parse all the data for me.

Update 1

elementsWithPossibleCCNumbers are XML Elements that contain 1 or MORE attributes that are 16 digits in length and are an integer. That being the case, you can't tell so I would change it to..

IEnumerable<XElement> elementsWithPossibleCCNumbers = 
        element.Descendants()
               .Where(d => d.Attributes()
                            .Where(a => a.Value.Length == 16)
                            .Where(a => int.TryParse(a.Value, out ccNumber))
                            .Count() == 1);  
                            // Where only 1 attribute is 16 length and an int

Extending it again...

IEnumerable<XAttribute> attributesWithPossibleCCNumbers =
        element.Descendants()
               .Where(d => d.Attributes()
                            .Where(a => a.Value.Length == 16)
                            .Where(a => int.TryParse(a.Value, out ccNumber))
                            .Count() == 1)
               .Select(e => e.Attributes()
                             .Where(a => a.Value.Length == 16)
                             .Where(a => int.TryParse(a.Value, out ccNumber))
                             .First());

Answer 3

Try using: <[^>]+[0-9]{16}[^>]+>

Edit: This might be more efficient- <([^>0-9]+)([0-9]{16})([^>]+)>

Answer 4

Don't use Regex to parse XML. It's not well suited to it.

How about using XmlDocument or XDocument instead?