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Tag: json

7 posts

2026-07-21 csharp dotnet-11 system-text-json

System.Text.Json Learns to Serialize C# Union Types in .NET 11 Preview 6

How System.Text.Json in .NET 11 Preview 6 serializes the new C# union types by writing the active case, and the JsonUnionAttribute and type-classifier APIs that handle ambiguous cases.

2026-06-23 how-to ef-core ef-core-11

How to map and query JSON columns in EF Core 11

Map a nested type to a single JSON column with ComplexProperty(...).ToJson(), let EF Core 11 store it in the native SQL Server 2025 json type, then query into it with LINQ that translates to JSON_VALUE, JSON_CONTAINS, and JSON_PATH_EXISTS.

2026-05-17 errors dart flutter

Fix: Unhandled Exception: FormatException: Unexpected character when parsing JSON in Dart

The fix in 30 seconds: your response body is not the JSON you think it is. Print the raw bytes, decode with utf8.decode(response.bodyBytes), and never feed an HTML error page or a BOM-prefixed string to jsonDecode.

2026-05-14 errors csharp dotnet

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.

2026-05-13 errors csharp dotnet

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.

2026-05-08 errors csharp dotnet

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.

2026-04-20 dotnet-11 ef-core-11 sql-server

EF Core 11 translates Contains to JSON_CONTAINS on SQL Server 2025

EF Core 11 auto-translates LINQ Contains over JSON collections to the new SQL Server 2025 JSON_CONTAINS function, and adds EF.Functions.JsonContains for path-scoped and mode-specific queries that can hit a JSON index.