我需要使用Kubernetes生成的YAML，并且希望能够使用C＃中类似XPath或jq的DSL表示法读取特定属性。
Kubernetes生成的YAML的结构和性质在大多数地方都是定义明确的，但是在某些情况下是任意的，并且来自用户输入，因此无法预先定义可以捕获整个结构的静态类型。 YAML。
在C＃中用于反序列化和读取YAML的最受欢迎的解决方案似乎是YamlDotNet，但它主要用于反序列化为完全类型的对象。
我宁愿不必定义一堆静态类型或进行大量繁琐的转换，而只需要获取一个或两个字段或在它们之间进行聚合。我理想的方法应该是：
var reader = new FileReader("my-file.yaml");
List<string> listOfPodNames = Yaml.Deserialize(reader)
.Query(".pods[*].name")
.AsList;
// expected result: list of all pod names as strings
是否可以使用YamlDotNet或C＃中的另一个类似且受支持的工具？
更新：我尝试了多种方法，但最后，最有效的方法是重新序列化为JSON，然后使用具有更好支持的Json.NET进行查询。
答案 0 :(得分：4)
在使用YamlDotNet反序列化机制而不指定目标类型时， 我们总是会得到一个词典（映射），一个 KeyValuePair列表（列表）或单个KeyValuePair /字符串（标量）。 KeyValuePair将包含另一个Dictionary，另一个List或实际值。
我们现在可以实现查询功能：
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>();
修改： 多个嵌套值
var data = new YamlQuery(yamlObject)
.On("ressources")
.On("pods")
.Get("name")
.ToList<string>();
工作示例：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.
...";
}
}
答案 1 :(得分：2)
您可以使用的另一种方法是将YAML转换为JSON，然后对其进行查询。尽管这将是一种更加耗时的方法，但是您可以肯定地比JSON轻松地查询JSON。
这是您可以怎么做
将YAML转换为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);
}
}
查询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"));
参考：-JSON.NET JObject - how do I get value from this nested JSON structure
答案 2 :(得分：1)
答案 3 :(得分：-1)
您对此有何看法？您只能投射所需的键：）
List<Dictionary<string, object>> mydic = new Deserializer().Deserialize(r);
foreach(Dictionary<string, object> wiii in mydic)
{
bool value = false;
if (wiii.ContainsKey("yourKeyname"))
value = (bool)wiii["yourKeyname"]; //<-- Here you can cast it in the type you wish
}
编辑
在代码开头添加using：
using YamlDotNet.Serialization;
using YamlDotNet.RepresentationModel;
使用that library added to your project并使用正确的YAML反序列化来编辑代码，应类似于初始源代码。