Language Integrated Query (LINQ) has revolutionized the way .NET developers interact with data. While many are familiar with its standard methods like Where, Select, and OrderBy, LINQ offers a wealth of advanced features that can significantly enhance performance, readability, and maintainability. In this article, we’ll explore some lesser-known but incredibly powerful LINQ features, complete with code examples and explanations to help you integrate them into your applications.

1️⃣HasQueryFilter (EF Core)

The HasQueryFilter method enables developers to define global query filters at the entity level, ensuring that certain data constraints are consistently enforced across all queries. This is particularly useful for implementing multi-tenancy, soft deletes, and role-based data access. Instead of applying Where clauses manually in every query, HasQueryFilter automates the process, reducing redundancy and minimizing the risk of missing important conditions.

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<User>()
        .HasQueryFilter(u => u.IsActive); // Automatically filters out inactive users
}

In this example, the IsActive filter is automatically applied to all queries involving the User entity, ensuring that inactive users are always excluded without requiring explicit Where conditions.

2️⃣AsSplitQuery (EF Core)

By default, when retrieving related entities, EF Core executes a single SQL query with joins, which can lead to inefficiencies like redundant data retrieval and Cartesian explosion — a performance issue that occurs when a query with multiple joins results in an excessive number of duplicate rows due to the way relational databases combine data. The AsSplitQuery() method allows EF Core to break these queries into multiple, more efficient SQL statements, reducing memory consumption and improving performance, especially for complex relationships.

var orders = context.Orders
    .Include(o => o.Customer)
    .Include(o => o.OrderItems)
    .AsSplitQuery()
    .ToList();

In this example, instead of executing a single large SQL query with multiple joins, AsSplitQuery() instructs EF Core to issue separate queries for each included navigation property. This reduces redundant data retrieval, minimizes the risk of Cartesian explosion, and improves performance, especially for complex relationships.

3️⃣ExecuteUpdate and ExecuteDelete (EF Core 7+)

Prior to EF Core 7, updating or deleting multiple records required fetching entities into memory, modifying them in code, and then saving the changes — an approach that was both inefficient and resource-intensive. With ExecuteUpdate and ExecuteDelete, EF Core enables direct bulk operations at the database level, eliminating the need to load entities into the application. These methods generate efficient SQL UPDATE and DELETE statements, significantly improving performance by reducing memory usage and database round trips. This makes them ideal for scenarios where large-scale modifications are needed, such as deactivating users, marking records as archived, or purging outdated data.

context.Users
    .Where(u => !u.IsActive)
    .ExecuteDelete();

In this example, this command deletes all inactive users directly in the database without first retrieving them, reducing memory usage and improving performance.

4️⃣ToQueryString (EF Core 5+)

Debugging LINQ queries can be challenging because Entity Framework Core translates them into SQL behind the scenes, making it difficult to understand how the query is actually executed at the database level. The ToQueryString() method, introduced in EF Core 5, allows developers to inspect the exact SQL that EF Core generates for a given LINQ query. This is invaluable for performance tuning, debugging complex queries, and ensuring that the generated SQL aligns with expectations. By using ToQueryString(), developers can optimize queries, avoid unintended behavior, and gain deeper insights into how EF Core interacts with the database.

var query = context.Users.Where(u => u.IsActive);
Console.WriteLine(query.ToQueryString());

In this example, the SQL generated by EF Core is outputted to the console, allowing developers to inspect and optimize database queries.

5️⃣Querying JSON Columns (EF Core 8+)

With the increasing adoption of hybrid relational-document database designs, many modern databases now support JSON columns, allowing developers to store semi-structured data within relational tables. EF Core 8 introduces built-in support for querying JSON data directly, enabling developers to filter, extract, and manipulate JSON fields using LINQ. This eliminates the need for raw SQL queries or additional deserialization steps, making it easier to work with dynamic data structures while still leveraging the power of relational databases. Whether storing user preferences, metadata, or nested configurations, querying JSON columns in EF Core 8 provides a flexible and efficient way to handle complex data models.

var users = context.Users
    .Where(u => EF.Functions.JsonValue(u.Metadata, "$.preferences.theme") == "dark")
    .ToList();

In this example, the query extracts and filters data from the Metadata JSON column, enabling structured data storage within a relational database.

LINQ is more than just a simple querying tool — it’s a powerful framework that, when used effectively, can significantly enhance the performance and maintainability of .NET applications. From global query filters to JSON column queries, these advanced features provide developers with the flexibility to build efficient and scalable applications. By incorporating these techniques into your workflow, you can unlock the full potential of LINQ and Entity Framework Core.