Fix: A possible object cycle was detected
System.Text.Json refuses to serialize graphs with back-references. Set ReferenceHandler.IgnoreCycles, project to a DTO, or mark the back-pointer with [JsonIgnore]. Preserve is a last resort.
Tag: system-text-json
17 posts · Page 2 of 2
Fix: System.Text.Json.JsonException: The JSON value could not be converted
System.Text.Json throws this when the incoming JSON token doesn't match the CLR target type. Match the JSON to the type, or register a JsonConverter or JsonSerializerOption that bridges them.
Fix: The JSON value could not be converted to System.DateTime
System.Text.Json only accepts ISO 8601 strings for DateTime. Send 2026-05-08T14:00:00Z or register a JsonConverter that parses your format. Empty strings and Unix timestamps both throw.
VSTest drops Newtonsoft.Json in .NET 11 Preview 4 and what breaks if you relied on it transitively
.NET 11 Preview 4 and Visual Studio 18.8 ship a VSTest that no longer flows Newtonsoft.Json into your test projects. Builds that quietly used the transitive copy will break with a single PackageReference fix.
How to write a custom JsonConverter in System.Text.Json
A complete guide to writing custom JsonConverter<T> for System.Text.Json in .NET 11: when you actually need one, how to navigate Utf8JsonReader correctly, how to handle generics with JsonConverterFactory, and how to stay AOT-friendly.
System.Text.Json in .NET 11 Preview 3 adds PascalCase and per-member naming policies
.NET 11 Preview 3 finishes the naming-policy story in System.Text.Json: JsonNamingPolicy.PascalCase, a member-level [JsonNamingPolicy] attribute, and a type-level [JsonIgnore] default for cleaner DTOs.
C# 14 idea: interceptors could make System.Text.Json source generation feel automatic
A community discussion proposed using C# 14 interceptors to rewrite JsonSerializer calls so they automatically use a generated JsonSerializerContext, keeping AOT-friendly source generation with cleaner call sites.