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_AddProjectableSelect appends Select<TEntity, TEntity>, so it only composes when the node really is a sequence of TEntity. It is not, whenever the caller already projected away from the entity root, and appending the rewrite anyway throws instead of no-oping: ArgumentException: Expression of type 'IQueryable<Dto>' cannot be used for parameter of type 'IQueryable<TEntity>' of method Select[TEntity,TEntity] _disableRootRewrite is meant to prevent this -- a Select sets it -- but EFNext#132 gave that same field a second job, the tracking decision. ExpressionVisitor walks outside-in, so in db.Set<T>().AsNoTracking().Where(...).Select(x => new Dto { ... }).ToList() the AsNoTracking node is visited last and clears the flag the Select set, re-enabling the rewrite against an IQueryable<Dto>. Any query that puts AsNoTracking before a projection to a DTO or an anonymous type throws, which is a common repository shape. Checking the node's own type is independent of visit order, so it holds whichever of the two flags wrote last. Deliberately an exact element-type match rather than an assignability check: IQueryable<out T> is covariant, so IQueryable<TEntity> is assignable from IQueryable<TDerived>, and rewriting there would re-project a derived entity as its base type. Tests: three new QueryRootTests cases covering AsNoTracking before a projection to an anonymous type, the same via the context's default tracking behaviour, and a projection that stays on the entity type (still rewritten). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
zmerdev
marked this pull request as ready for review
September 25, 2026 20:49
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Fix for issue #223
This pull request improves the handling of query root rewrites in the
ProjectableExpressionReplacerby ensuring that projection rewrites are only applied when the query result is exactly the entity type, preventing invalid rewrites for projections to anonymous or DTO types. It also adds comprehensive tests to verify these scenarios across multiple .NET versions.Query root rewrite correctness
_IsSequenceOfEntity) in_AddProjectableSelectto ensure that the projectable select is only appended when the queryable sequence is exactly of the entity type, preventing errors when projecting to anonymous or DTO types. [1] [2]_queryableElementTypeCache) and helper methods to efficiently determine the element type ofIQueryable<T>sequences. [1] [2]Test coverage
AsNoTracking()and projections to both anonymous types and entity types, ensuring the rewrite is only applied when appropriate.