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2026-10-25 dart flutter json

How to serialize and deserialize a Dart sealed class hierarchy to and from JSON

Put a discriminator field in the JSON, switch on it in a factory on the sealed base, and switch on the subtype to write it back. Three working versions on Dart 3.13.7: hand-written pattern matching, json_serializable 6.15.2, and Freezed 4.0.3 with unionKey and fallbackUnion, plus the gotchas each one hides.

2026-09-27 ef-core ef-core-11 sql-server

How to add a unique index on a JSON-mapped property in EF Core 11 (SQL Server and SQLite)

HasIndex(...).IsUnique() on a ToJson() member does not enforce uniqueness in EF Core 11 RC 1: SQL Server drops IsUnique and SQLite indexes the whole document. Expose the JSON value as a computed column and put the unique index on that instead.

2026-09-23 system-text-json csharp dotnet-10

How to serialize public fields like Vector3 and Quaternion with System.Text.Json

System.Text.Json writes Vector3 as {} and Quaternion as {"IsIdentity":false} because they store data in public fields. Here is how IncludeFields, a custom converter, a resolver modifier and source generation fix it, measured on .NET 10 and .NET 11 RC 1.

2026-09-21 ef-core ef-core-10 postgresql

How to atomically append to a PostgreSQL jsonb array with EF Core and Npgsql

Loading an entity, calling List.Add, and saving rewrites the whole jsonb document and silently loses concurrent appends. Push the append into one UPDATE with the jsonb || operator, either through ExecuteSqlAsync or a mapped function inside ExecuteUpdateAsync, and make it idempotent with a @> guard.

2026-09-12 comparison ef-core ef-core-11

Native json column vs nvarchar(max) for storing JSON in SQL Server with EF Core 11

Use the native json type on SQL Server 2025 and Azure SQL: EF Core 11 gets JSON_CONTAINS, typed JSON_VALUE, in-place modify() and JSON indexes out of it. Stay on nvarchar(max) for SQL Server 2019/2022, legacy tooling, or a schema you must be able to roll back.

2026-09-09 errors ef-core ef-core-11

Fix: AS JSON option can be specified only for column of nvarchar(max) type in WITH clause

EF Core emits [col] json '$.path' AS JSON inside OPENJSON WITH, which Azure SQL rejects with Msg 13618. Upgrade to EF Core 10.0.11+, or drop the provider compatibility level to 160.

2026-09-09 errors ef-core ef-core-11

Fix: Complex entry original ordinal '-1' is invalid when saving a ToJson complex collection

Upgrade Microsoft.EntityFrameworkCore to 10.0.10 or later. Before that, growing a nested collection under a second ToJson complex property crashed SaveChanges.

2026-09-09 errors ef-core ef-core-11

Fix: The complex type collection must be initialized to a non-null value

On EF Core 10.0.x, nulling a complex property that holds a two-element collection inside a ToJson complex collection breaks DetectChanges. Fixed in 11.0.0-rc.1.

2026-08-16 system-text-json csharp csharp-14

How to make System.Text.Json ignore a property that has the required modifier

[JsonIgnore] on a required member throws InvalidOperationException: marked required but does not specify a setter. Here is why the two features collide and the four ways to ignore the property anyway, measured on .NET 10.

2026-07-29 errors mcp claude-code

Fix: a Windows path in your agent config silently turns into a tab, a newline, or a Chinese character

Folder names starting with t, b, n, r or u make a Windows path parse cleanly as JSON and still resolve wrong. Use forward slashes or double every backslash.