字典 <string, List<ClassObj> &gt; LINQ To XML查询

Question

I try to put my XML File into a Dictionary with Generic List. How I can merge correct the query List to my dictionary with correct key? Instead of .ToList() .ToDictionary is not possible?

<?xml version="1.0"?>
<customers>
  <cust ID="1" DeviceID="1" Name="Bob" Latitude="10" Longitude="58" Device="HW1.0"> </cust>
  <cust ID="2" DeviceID="2" Name="Jack" Latitude="28" Longitude="20" Device="HW2.2"> </cust>
</customers>

//XML attribute Name is Dict Key

public class Customers
{
    public int Longitude { get; set; }
    public int Latitude { get; set; }
    public int DeviceID { get; set; }
    public string Device { get; set; }
}

class Program
{

    private static Dictionary<string, List<Customers>> ReadXmlToDict(string filename)
    {
        // Should be Key = Xml Attribute Name Value, List of class 
        Dictionary<string, List<Customers>> dict = new Dictionary<string, List<Customers>>();

        XDocument xdoc = XDocument.Load(filename);
        var querylist = (from row in xdoc.Descendants("cust")
                         select new Customers()
                         {
                             //Name = (string)row.Attribute("Name"),  // Wrong here should be the Dic key
                             DeviceID = (int)row.Attribute("DeviceID"), // list value
                             Longitude = (int)row.Attribute("Longitude"),  // list value
                             Latitude = (int)row.Attribute("Latitude"), // list value
                             Device = (string)row.Attribute("Device")  // list value
                         }).ToList();

        return null; // null for test To.List and not Dict
    }

Answer 1

This is how I would implement it, I think it accomplishes what you're looking for. You have a class called Customers and then want to store a list of those customers with a single key...I don't follow that logic.

I created a class called Customer , which houses the information for a singular customer. Since you're returning a Dictionary<string, Customer> , where the string is the unique attribute Name in the xml, there is no use case for the value of your dictionary being a List<Customer> . Perhaps if you have multiple customers under the same name, you would use this, but why not then make the key the (I assume) truly unique identifier, the DeviceID ?

namespace TestConsole
{
    class Customer
    {
        public int DeviceID;
        public int Longitude;
        public int Latitude;
        public string Device;
    }
    class Program
    {

        private static Dictionary<string, Customer> ReadXmlToDictionary(string filename)
        {
            var dict = new Dictionary<string, Customer>();

            var doc = XDocument.Load(@"C:\test.xml");

            dict = doc.Descendants("cust")
                .ToDictionary(
                    row => (string)row.Attribute("Name"),
                    row => new Customer {
                        Device = (string)row.Attribute("Device"),
                        DeviceID = (int)row.Attribute("DeviceID"),
                        Latitude = (int)row.Attribute("Latitude"),
                        Longitude = (int)row.Attribute("Longitude")
                });

            return dict;
        }

        static void Main(string[] args)
        {
            ReadXmlToDictionary(null);
        }
    }
}

EDIT: Thought the performance related answer was interesting, so decided to try it out for this single level xml (using ID as the unique identifier). Here are the results:

1019 Descendants took 0.0030257 seconds.
1019 Elements took 0.0028348 seconds.
10000 Descendants took 0.0098942 seconds.
10000 Elements took 0.0101478 seconds.
100000 Descendants took 0.0873025 seconds.
100000 Elements took 0.1223577 seconds.

EDIT : After creating your xsd, and generating a class from it, you would then use it as such:

var parsed = XDocument.Parse(doc.ToString());

var serializer = new XmlSerializer(typeof(Xsds.customers));

var typedPayload = serializer.Deserialize(doc.Root.CreateReader());

var xmlAsClass = (TestConsole.Xsds.customers)typedPayload;

dict = xmlAsClass.cust
    .ToDictionary(
        row => (int)row.ID,
        row => new Customer {
            Device = row.Device,
            DeviceID = row.DeviceID,
            Latitude = row.Latitude,
            Longitude = row.Longitude,
            Name = row.Name
        });

Answer 2

You can do it easily by using ToDictionary() extension method. But performance wise, it is far better to use Elements() method rather than Descendants() ; For further reading please read this blog post: WHY (OR WHEN) YOU SHOULD/SHOULDN'T USE DESCENDANTS() METHOD

And your query will look like this:

var customersDictionary = 
    xDoc.Root
        .Elements("cust")
        .ToDictionary(xe => 
                        xe.Attribute("Name").Value, xe => 
                        new Customers
                        {
                            DeviceID = (int)xe.Attribute("DeviceID"), 
                            Longitude = (int)xe.Attribute("Longitude"),  
                            Latitude = (int)xe.Attribute("Latitude"),
                            Device = (string)xe.Attribute("Device")
                        });