AL0027 - Avoid legacy JSON library

Replace legacy JSON libraries with System.Text.Json for better performance and native .NET support

Source: AL0027AvoidNewtonsoftJsonAnalyzer.cs

Description

The legacy JSON library (Newtonsoft.Json) should be replaced with System.Text.Json for better performance and native .NET support.

This rule only triggers when System.Text.Json is available in the project, making migration possible.

Bad Code

using Newtonsoft.Json;

var json = JsonConvert.SerializeObject(obj);
var obj = JsonConvert.DeserializeObject<MyClass>(json);
var jObject = JObject.Parse(json);

Good Code

using System.Text.Json;

var json = JsonSerializer.Serialize(obj);
var obj = JsonSerializer.Deserialize<MyClass>(json);
var doc = JsonDocument.Parse(json);

Properties

• Category: Usage
• Severity: Warning
• Enabled by default: True
• Code fix available: False

Configuration

dotnet_diagnostic.AL0027.severity = warning

Notes

System.Text.Json is the recommended JSON library for .NET applications. It offers:

• Better performance (faster serialization/deserialization)
• Lower memory allocations
• Native integration with ASP.NET Core
• Source generator support for AOT compilation