How to get XML into a dictionary in c#

Question

I have the following XML:

<Axis>
    <Collections>
        <Collection>
            <Client>
                <Name>Client 1</Name> 
                <Value>345</Value> 
            </Client>
        </Collection>
        <Collection>
            <Client>
                <Name>Client 1</Name> 
                <Value>4532</Value> 
            </Client>
        </Collection>
        <Collection>
            <Client>
                <Name>Client 1</Name> 
                <Value>235</Value> 
            </Client>
        </Collection>
        <Collection>
            <Client>
                <Name>Client 1</Name> 
                <Value>8756</Value> 
            </Client>
        </Collection>
        <Collection>
            <Client>
                <Name>Client 1</Name> 
                <Value>76</Value> 
            </Client>
        </Collection>
    </Collections>
    <Collections>
        <Collection>
            <Client>
                <Name>Client 2</Name> 
                <Value>56</Value> 
            </Client>
        </Collection>
        <Collection>
            <Client>
                <Name>Client 2</Name> 
                <Value>43</Value> 
            </Client>
        </Collection>
        <Collection>
            <Client>
                <Name>Client 2</Name> 
                <Value>34</Value> 
            </Client>
        </Collection>
        <Collection>
            <Client>
                <Name>Client 3</Name> 
                <Value>42</Value> 
            </Client>
        </Collection>
        <Collection>
            <Client>
                <Name>Client 3</Name> 
                <Value>23</Value> 
            </Client>
        </Collection>
    </Collections>
</Axis>

and I would like to store some of this in a dictionary Dictionary<string, List<string>> where the key is the name element and the value is a list of the Value elements.

I have mucked around with a bit of LINQ, but I have not been able to work out the dictionary part.

I have been able to get one element into a list:

myDoc.XPathSelectElements("//Axis/Collections/Collection/Client/Value")
     .Select(v => v.Value)
     .ToList();

Jon Skeet · Accepted Answer · 2014-10-22 12:49:44Z

I would suggest:

Not using XPath to select elements, but using the Elements() method (etc) instead
Using a lookup instead of a Dictionary<string, List<string>>, via ToLookup. A lookup is like a dictionary with multiple values per key, but slightly simpler to handle (as it returns an empty sequence if you ask for a missing key) and much easier to construct.

So the code would look something like:

var lookup = doc.Root
                .Elements("Collections")
                .Elements("Collection")
                .Elements("Client")
                .ToLookup(x => (string) x.Element("Name"),
                          x => (string) x.Element("Value"));

You can then do things like:

foreach (var value in lookup["Client 1"])
{
    ...
}

An alternative to all the Elements() calls would be to use Descendants(), e.g.

var lookup = doc.Descendants("Client")
                .ToLookup(x => (string) x.Element("Name"),
                          x => (string) x.Element("Value"));

atom.gregg · Accepted Answer · 2014-10-22 12:50:26Z

I would suggest using a construct that allows you to query, my personal favourite for querying XML is Linq to XML.

First, get what you're after (the name and value).
Then, group that on the name
Finally, project to your target type (a dictionary)

Example (you can copy and paste this straight into LinqPad):

var xml = @"<Axis>
<Collections>
   <Collection>
       <Client>
           <Name>Client 1</Name> 
           <Value>345</Value> 
       </Client>
   </Collection>
   <Collection>
       <Client>
           <Name>Client 1</Name> 
           <Value>4532</Value> 
       </Client>
   </Collection>
   <Collection>
       <Client>
           <Name>Client 1</Name> 
           <Value>235</Value> 
       </Client>
   </Collection>
   <Collection>
       <Client>
           <Name>Client 1</Name> 
           <Value>8756</Value> 
       </Client>
   </Collection>
   <Collection>
       <Client>
           <Name>Client 1</Name> 
           <Value>76</Value> 
       </Client>
   </Collection>
</Collections>
<Collections>
   <Collection>
       <Client>
           <Name>Client 2</Name> 
           <Value>56</Value> 
       </Client>
   </Collection>
   <Collection>
       <Client>
           <Name>Client 2</Name> 
           <Value>43</Value> 
       </Client>
   </Collection>
   <Collection>
       <Client>
           <Name>Client 2</Name> 
           <Value>34</Value> 
       </Client>
   </Collection>
   <Collection>
       <Client>
           <Name>Client 3</Name> 
           <Value>42</Value> 
       </Client>
   </Collection>
   <Collection>
       <Client>
           <Name>Client 3</Name> 
           <Value>23</Value> 
       </Client>
   </Collection>
</Collections>
</Axis>";

var doc = XDocument.Parse(xml);
var dict = (from row in doc.Root.Descendants("Client")
            let name = row.Element("Name").Value
            let value = row.Element("Value").Value
            group value by name into grp
            select new { grp.Key, Values = grp.ToList() }).ToDictionary(d => d.Key, d => d.Values);
dict.Dump();

Martin Milan · Accepted Answer · 2014-10-22 13:11:01Z

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml.Linq;

namespace XMLToDictionary
{
    class Program
    {
        static void Main(string[] args)
        {
            var doc = XDocument.Load("c:\\Test.xml");

            var clients = doc.Descendants().Where(e => e.Name.LocalName == "Client").ToList();
            Dictionary<string, List<string>> dic = new Dictionary<string, List<string>>();
            foreach (var client in clients)
            {
                string key = client.Elements().First(e => e.Name.LocalName == "Name").Value;
                string val = client.Elements().First(e => e.Name.LocalName == "Value").Value;
                if (!dic.ContainsKey(key))
                {
                    dic[key] = new List<string>();
                }
                dic[key].Add(val);
            }


        }
    }
}

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