如何用Newtonsoft.Json.Linq获取JSON中Data节点下带Symbol属性的元素？

Hey Ronald, no worries at all—let's break this down step by step so you can easily grab those elements with the Symbol property using Newtonsoft.Json.Linq (often called JLinq). Here's a straightforward approach:

Step 1: Parse the JSON into a JObject #

First, we need to convert your JSON string into a JObject instance, which lets us navigate and query the JSON structure easily.

Step 2: Access the Data Node #

Next, we'll pull out the Data node from the root JObject. We'll cast it to JObject to ensure we're working with a collection of key-value pairs.

Step 3: Filter Elements with the Symbol Property #

We'll iterate over all child elements in the Data node, then filter out any that don't have the Symbol property. Since each entry in Data is a key-value pair (like "42": { ... }), we'll use Children<JProperty> to access each entry, then extract its value as a JObject.

Full Code Example #

using Newtonsoft.Json.Linq;
using System;
using System.Linq;

class Program
{
    static void Main()
    {
        // Your original JSON string
        string json = @"{ 
            ""prop1"": ""bla"", 
            ""propn"": ""bla"", 
            ""Data"": { 
                ""42"": { ""prop1"": ""bla"", ""prop2"": ""bla"", ""Symbol"": ""42"" }, 
                ""abc"": { ""prop1"": ""bla"", ""prop2"": ""bla"", ""Symbol"": ""abc"" } 
            }, 
            ""Type"": 100 
        }";

        // Parse the JSON into a JObject
        JObject rootObj = JObject.Parse(json);

        // Get the Data node (cast to JObject to ensure we can iterate over its children)
        if (rootObj["Data"] is JObject dataNode)
        {
            // Filter all elements in Data that have a Symbol property
            var elementsWithSymbol = dataNode.Children<JProperty>()
                                            .Select(prop => prop.Value as JObject)
                                            .Where(obj => obj != null && obj.ContainsKey("Symbol"));

            // Process each matching element
            foreach (var element in elementsWithSymbol)
            {
                string symbolValue = element["Symbol"].ToString();
                string prop1Value = element["prop1"].ToString();
                
                Console.WriteLine($"Found element with Symbol: {symbolValue} | Prop1: {prop1Value}");
            }
        }
        else
        {
            Console.WriteLine("Data node not found or is not an object.");
        }
    }
}

Key Notes: #

• Null Safety: We check if rootObj["Data"] is a valid JObject and if each child value is a JObject to avoid null reference exceptions.
• Flexible Filtering: The Where clause lets you add extra conditions if needed (e.g., checking if Symbol has a specific value).
• Accessing Values: Use ToString() for string values, or ToObject<T>() if you need to convert to other types (like int for a numeric Symbol).

If you need to do something specific with these elements (like map them to a C# class), you can extend this code by using element.ToObject<YourClass>() where YourClass has properties matching the JSON structure.

内容的提问来源于stack exchange，提问作者Ronald