With C#, is querying YAML possible without defining lots of types?
When using YamlDotNet Deserializing mechanism without specifying a target type, we always get a either a Dictionary (mapping),a List of KeyValuePairs (list) or a single KeyValuePair/string (scalar). The KeyValuePairs will either contain another Dictionary, another List or the actual value.
We now can implement a query functionality:
var data = new YamlQuery(yamlObject)
.On("pods") // parent
// this functionality could be implemented as well wihtout much effort
//.Where("ignore").Equals(true)
.Get("name") // propery
.ToList<string>();
Edit: Multiple nested values
var data = new YamlQuery(yamlObject)
.On("ressources")
.On("pods")
.Get("name")
.ToList<string>();
Working example: https://dotnetfiddle.net/uNQPyl
using System.IO;
using System;
using System.Linq;
using YamlDotNet.Serialization;
using System.Collections.Generic;
using YamlDotNet.RepresentationModel;
namespace ConsoleApp1
{
public class Program
{
public static void Main()
{
object yamlObject;
using (var r = new StringReader(Program.Document))
yamlObject = new Deserializer().Deserialize(r);
var data = new YamlQuery(yamlObject)
.On("pods")
.Get("name")
.ToList<string>();
Console.WriteLine("all names of pods");
Console.WriteLine(string.Join(",", data));
data = new YamlQuery(yamlObject)
.On("ressources")
.On("pods")
.Get("name")
.ToList<string>();
Console.WriteLine("all names of pods in ressources");
Console.WriteLine(string.Join(",", data));
}
public class YamlQuery
{
private object yamlDic;
private string key;
private object current;
public YamlQuery(object yamlDic)
{
this.yamlDic = yamlDic;
}
public YamlQuery On(string key)
{
this.key = key;
this.current = query<object>(this.current ?? this.yamlDic, this.key, null);
return this;
}
public YamlQuery Get(string prop)
{
if (this.current == null)
throw new InvalidOperationException();
this.current = query<object>(this.current, null, prop, this.key);
return this;
}
public List<T> ToList<T>()
{
if (this.current == null)
throw new InvalidOperationException();
return (this.current as List<object>).Cast<T>().ToList();
}
private IEnumerable<T> query<T>(object _dic, string key, string prop, string fromKey = null)
{
var result = new List<T>();
if (_dic == null)
return result;
if (typeof(IDictionary<object, object>).IsAssignableFrom(_dic.GetType()))
{
var dic = (IDictionary<object, object>)_dic;
var d = dic.Cast<KeyValuePair<object, object>>();
foreach (var dd in d)
{
if (dd.Key as string == key)
{
if (prop == null)
{
result.Add((T)dd.Value);
} else
{
result.AddRange(query<T>(dd.Value, key, prop, dd.Key as string));
}
}
else if (fromKey == key && dd.Key as string == prop)
{
result.Add((T)dd.Value);
}
else
{
result.AddRange(query<T>(dd.Value, key, prop, dd.Key as string));
}
}
}
else if (typeof(IEnumerable<object>).IsAssignableFrom(_dic.GetType()))
{
var t = (IEnumerable<object>)_dic;
foreach (var tt in t)
{
result.AddRange(query<T>(tt, key, prop, key));
}
}
return result;
}
}
private const string Document = @"---
receipt: Oz-Ware Purchase Invoice
date: 2007-08-06
customer:
given: Dorothy
family: Gale
pods:
- name: pod1
descrip: Water Bucket (Filled)
price: 1.47
quantity: 4
- name: pod2
descrip: High Heeled ""Ruby"" Slippers
price: 100.27
quantity: 1
- name: pod3
descrip: High Heeled ""Ruby"" Slippers
ignore: true
quantity: 1
bill-to: &id001
street: |-
123 Tornado Alley
Suite 16
city: East Westville
state: KS
pods:
- name: pod4
descrip: High Heeled ""Ruby"" Slippers
price: 100.27
quantity:
ressources:
- pids:
- id: 1
- name: pid
- pods:
- name: pod5
descrip: High Heeled ""Ruby"" Slippers
price: 100.27
quantity:
- name: pod6
descrip: High Heeled ""Ruby"" Slippers
price: 100.27
quantity:
specialDelivery: >
Follow the Yellow Brick
Road to the Emerald City.
Pay no attention to the
man behind the curtain.
...";
}
}
There is the following GitHub project: YamlDotNet.Dynamic
It leverages the dynamic type in C# and therefore you don't need to define static types.
A different approach would be to convert into Json and use Newtonsoft.Json, which supports dynamic types, too.
Another approach you can use is converting YAML to JSON and then query it. though it would be a more time-consuming approach you can surely query a JSON easily then YAML.
Here is how you can do it
Convert YAML To JSON
public class ConvertYamlToJson
{
private readonly ITestOutputHelper output;
public ConvertYamlToJson(ITestOutputHelper output)
{
this.output = output;
}
[Sample(
DisplayName = "Convert YAML to JSON",
Description = "Shows how to convert a YAML document to JSON."
)]
public void Main()
{
// convert string/file to YAML object
var r = new StringReader(@"
scalar: a scalar
sequence:
- one
- two
");
var deserializer = new DeserializerBuilder().Build();
var yamlObject = deserializer.Deserialize(r);
var serializer = new SerializerBuilder()
.JsonCompatible()
.Build();
var json = serializer.Serialize(yamlObject);
output.WriteLine(json);
}
}
Ref:- Convert YAML to JSON
Query JSON
string json = @"
{
""client_id"": ""26075235"",
""client_version"": ""1.0.0"",
""event"": ""app.uninstall"",
""timestamp"": 1478741247,
""data"": {
""user_id"": ""62581379"",
""site_id"": ""837771289247593785"",
""platform_app_id"": ""26075235""
}
}";
JObject jo = JObject.Parse(json);
Console.WriteLine("User ID: " + (string)jo.SelectToken("data.user_id"));
Ref:- JSON.NET JObject - how do I get value from this nested JSON structure