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EF Core 10 업데이트 살펴보기: LeftJoin과 벡터 검색 실전 적용 가이드

Exploring EF Core 10 Updates: A Practical Guide to LeftJoin and Vector Search

Released alongside .NET 10, Entity Framework Core 10 focuses on alleviating long-standing frustrations that C# developers previously had to circumvent. It includes features that simplify complex query writing and allow modern AI workloads to be processed at the data layer.

Here, we summarize the new query methods, vector search capabilities, and key breaking changes to watch out for when upgrading your existing projects.

The Long-Awaited LeftJoin LINQ Operator

In previous versions of EF Core, writing an outer join required calling GroupJoin followed by a chained call to DefaultIfEmpty and SelectMany. This made the code unnecessarily long and created a structure that was difficult for beginners to grasp intuitively.

To improve query readability in EF Core 10, LeftJoin and RightJoin operators are now natively supported as standard LINQ APIs. This allows for concise syntax even in scenarios where navigating table relationship properties directly is difficult.

Below is an example of using LeftJoin in EF Core 10.

csharp

// EF Core 10 기준
var query = dbContext.Users
    .LeftJoin(
        dbContext.Orders,
        user => user.Id,
        order => order.UserId,
        (user, order) => new { user.Name, OrderAmount = (decimal?)order.Amount }
    )
    .ToListAsync();

You can construct intuitive LINQ code that corresponds one-to-one with the SQL LEFT JOIN syntax without unnecessary nested lambdas.

SqlVector and Native Vector Search Support

With the increasing adoption of Retrieval-Augmented Generation (RAG) architectures that store embedding vectors and perform similarity searches, EF Core 10 now officially supports database-level vector operations.

SqlVector<T> format and the EF.Functions.VectorDistance method allow for similarity-based lookups in Azure SQL and SQL Server 2025 environments without needing third-party libraries.

csharp

// EF Core 10 기준
var queryVector = new SqlVector<float>(userEmbedding);

var documents = await dbContext.Documents
    .OrderBy(doc => EF.Functions.VectorDistance("cosine", doc.Embedding, queryVector))
    .Take(5)
    .ToListAsync();

Since cosine similarity calculations are optimized and executed within the database engine, there is no need to download large-scale vectors to the backend application for processing.

Support for Non-Expression Lambdas in ExecuteUpdateAsync

The ExecuteUpdateAsync method, used for bulk data updates, has also become more flexible. In previous versions, strict limitations within lambda expressions made it difficult to combine dynamic conditions or conditional updates across multiple columns.

EF Core 10 now accepts standard non-expression lambda syntax, allowing you to configure update targets more dynamically based on conditional branching.

Breaking Changes to Check When Migrating

There are several changes you must verify before migrating to EF Core 10.

Runtime requirements are now limited to the .NET 10 SDK and runtime. Compatibility with older runtime versions is not supported, so you must update the framework target for your entire solution.

For multi-targeting projects, you must explicitly specify the dotnet-ef option when running --framework CLI tool commands. If omitted, the migration tool will fail to identify the target and return an error.

When using SQL Server 2025 or Azure SQL with a compatibility level of 170 or higher, the default collection data type mapping automatically changes from nvarchar(max) to the native json type. You should review your database compatibility settings when migrating existing JSON-serialized column data.

Practical Implementation Recommendations

For simple CRUD-focused applications, it is more stable to align with your team's .NET 10 adoption roadmap rather than migrating immediately.

However, if you are building a vector search pipeline based on SQL Server 2025 or working on a backend service with many complex statistical LINQ join queries where readability improvements are urgent, we recommend testing the transition to EF Core 10 to take advantage of simplified queries early.

lelearn.microsoft.com

Microsoft Learn: What's New in EF Core 10

Overview of new features in EF Core 10