Question

I am using following code to get List from xml file –

    public static List<T> GetListFromXml<T>(string filePath)
    {
        using (TextReader reader = new StreamReader(filePath))
        {
            XmlSerializer serializer = new XmlSerializer(typeof(List<T>));
            return (List<T>) serializer.Deserialize(reader);
        }
    }

However, I also need a way of filtering records where I can filter list by –
– no. of records to take from xml file
– filter by a particular node value
So signature of above method will change to –

    public static List<T> GetListFromXml<T>(string filePath, 
                                            int listCount, 
                                            string filterbyNode, 
                                            string filterByValue);

Please guide me if I can filter directly from XML file or I should filter from returned list?

---

P.S.

The xml file mentioned above is also created from code using –

    public static void WriteListToXml<T>(List<T> list, string filePath)
    {
        using (TextWriter writer = new StreamWriter(filePath))
        {
            XmlSerializer serializer = new XmlSerializer(typeof(List<T>));
            serializer.Serialize(writer, list);
        }
    }

Why I am saving my custom collection returned from database to xml file – because I want to process only a batch of records at a time.

and XML file snippet (generated from above code) –

<?xml version="1.0" encoding="utf-8"?>
<ArrayOfClassifiedLocation xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <CLocation>
    <CId>5726</CId>
    <Long>0</Long>
    <Lat>0</Lat>
    <Postcode>ZZ1 5ZZ</Postcode>
    <Street />
    <Town />
  </CLocation>
  <CLocation>
    <CId>5736</CId>
    <Long>0</Long>
    <Lat>0</Lat>
    <Postcode>ZZ1 5ZZ</Postcode>
    <Street />
    <Town />
  </CLocation>
</ArrayOfClassifiedLocation>

Answer 1

Below an example of LINQ-to-XML query which consider cid paremeter filter. If you put empty string in cidFilter the query would return all entries:

// you can use Parse() method:
// XDocument loaded = XDocument.Parse(xmlString);
XDocument loaded = XDocument.Load("c:\\temp\\testxl.xml");

// return only entry fith CID == 5726
string cidFilter = "5726";
var filteredItems =
loaded.Descendants("CLocation")
    .Select((w, i) =>
            new
                {
                    Index = i,
                    CID = w.Descendants("CId").FirstOrDefault().Value,
                    PostCode = w.Descendants("Postcode").FirstOrDefault().Value
                })
    .Where(item => String.IsNullOrEmpty(cidFilter) || item.CID == cidFilter)
    .ToList();

int itemsCount = filteredItems.Count();