Скачать или смотреть How to Parse JSON from a String with Trailing Content Using System.Text.Json

Learn how to effectively parse a JSON document embedded in a string with unexpected trailing content using System.Text.Json in C# .
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This video is based on the question https://stackoverflow.com/q/64041939/ asked by the user 'gregsdennis' ( https://stackoverflow.com/u/878701/ ) and on the answer https://stackoverflow.com/a/64099104/ provided by the user 'gregsdennis' ( https://stackoverflow.com/u/878701/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Handling JSON Parsing When Faced with Unexpected Trailing Content

Parsing JSON can be straightforward when working with clean data. However, what happens when that JSON string is unexpectedly followed by unrelated content? This problem frequently arises in various applications, especially when you have limited control over the data being processed. In this post, we'll explore a method to parse JSON documents that exist within sprawling strings, specifically using System.Text.Json in C# .

Understanding the Problem

Imagine a scenario where you receive a string input containing a valid JSON value but is immediately followed by irrelevant details or text. Here are some examples:

Input: "true and some more"

Output: <true>

Input: "5.6/7"

Output: <5.6>

Input: "{"key": "value"}, then the end"

Output: <{"key": "value"}>

Attempting to parse these strings using the built-in methods in JsonDocument often leads to errors similar to:

[[See Video to Reveal this Text or Code Snippet]]

The challenge lies in the trailing content, which disrupts the parsing process. This is where a custom solution becomes necessary.

Developing a Solution

While there are built-in solutions, we require a custom approach to effectively isolate and parse the JSON embedded within the string. Here is a step-by-step breakdown of our proposed solution:

Step 1: Define the Parsing Method

Create a static method named TryParseJsonElement which will take a ReadOnlySpan<char> and an integer reference, along with an output parameter for the resulting JsonElement.

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Implement Helpers to Parse Values

The core component of the TryParseJsonElement method is breaking down the parsing logic into smaller helper methods such as ParseNumber, ParseString, and ParseCollection. These functions will help identify valid JSON structures while managing the characters as they are iterated.

Step 3: Leveraging the Method

Once the parsing method is defined, you can easily utilize it to parse strings with specific custom JSON handling. This is especially important in scenarios where embedded JSON is not the only content present in the string.

Conclusion

The task of parsing JSON values embedded in strings containing irrelevant trailing content can indeed be complex. However, using a custom method as outlined above allows you to isolate valid JSON structures and process them correctly using System.Text.Json. By following the steps outlined, you can effectively parse strings without falling victim to exceptions related to unexpected trailing content.

Happy coding!