Master JSON Parsing in C#: Generate C# Classes from Complex JSON Without External Packages

Working with JSON data is a common task for any C# developer, especially when integrating with APIs or handling configuration files. While there are robust libraries like Json.NET (Newtonsoft.Json) and System.Text.Json to handle JSON parsing, there might be scenarios where you need to work with plain C# without external dependencies.

In this article, we'll explore how to manually parse a JSON object string and dynamically generate corresponding C# classes, all without relying on any external libraries.

Understanding the Task

To generate C# classes from a JSON string, we need to:

• Manually parse the JSON string using C# string operations.
• Identify the data types and structure of the JSON.
• Generate C# classes that match the JSON structure.

We will achieve this by using basic C# techniques such as loops, conditional checks, and string manipulation.

Step-by-Step Solution

Example JSON String

Let's use the following JSON object as an example:

This JSON string contains nested objects, arrays, and various data types (string, int, double, boolean). The goal is to generate a set of C# classes that accurately represent this JSON structure.

C# Code to Parse JSON and Generate Classes

The following C# code manually parses the JSON string and dynamically generates the necessary classes:

How the Code Works

1. Main Method:

• Initializes the JSON string and a dictionary to store generated class definitions.
• Calls ParseJsonObject to begin processing the JSON string.

2. ParseJsonObject Method:

• Cleans up the JSON string by removing outer braces and whitespace.
• Splits the JSON string into lines of key-value pairs and iterates over them.
• Determines each property's type using DeterminePropertyType and constructs the C# class definition.

3. DeterminePropertyType Method:

• Identifies the data type of each JSON property (string, int, bool, double, or a nested object/array).
• Recursively generates C# classes for nested objects and arrays.

Running the Code

This code can be run in any .NET environment. Upon execution, it will output the necessary C# classes to represent the JSON structure, like the following:

Example Output

Handling Deeply Nested Structures

This approach handles any level of nested JSON objects by recursively calling ParseJsonObject for each nested object or array, dynamically generating C# classes based on the JSON's structure. The use of a dictionary ensures that each class is generated only once, even if there are repeated structures.

Key Points to Consider

• Simplicity: This approach uses only built-in C# functionalities, making it ideal for environments where you cannot use external libraries.
• Efficiency: Although this method is less efficient than using dedicated JSON parsers, it provides valuable insight into how JSON parsing works.
• Limitations: The code assumes a simplified JSON structure and may need additional handling for more complex JSON strings (e.g., handling of escaped characters or mixed-type arrays).

Conclusion

Generating C# classes from JSON data without external libraries is entirely possible using plain C# techniques. This approach is useful in scenarios where external dependencies are not an option or when you want to learn how JSON parsing works at a fundamental level. With the steps outlined in this guide, you can manually parse JSON strings and dynamically generate the corresponding C# classes for any JSON structure.

By understanding this process, you'll be better equipped to handle JSON data in various environments and scenarios.