Ef core query. Distance(myLocation) descending select f).
Ef core query 01/26/2025 04/08/2021 by Mak. The most common use cases for this feature include properties that indicate that an entity instance is deleted, or not otherwise active, and a tenant identifier in an application that I need some sample code for my project. EntityFrameworkCore: "NeinLinq extends LINQ providers such as Entity Framework to enable reusing functions, rewriting queries, and building dynamic queries using translatable predicates and selectors. 10. Property in EF Core queries for more information and examples. 1. Set<string>() . Since EF 7 is renamed to Entity Framework Core I EF Core has a concept of mixed client/database evaluation in LINQ queries which allows them to release EF Core versions with incomplete/very inefficient query processing like in your case. Net 5+ but the same generic concept can still be applied) The Distinct operator instructs EF Core to select unique records. In addition to entity types, an EF Core model can contain query types, which can be used to carry out database queries against data that isn't mapped to entity types. NET language of choice) to write strongly typed queries based on your derived context and entity classes. 1. If you're like me, you've probably spent countless EF Core is getting many new and exciting features in the upcoming version. Custom methods for obvious reasons cannot be translated to SQL. Select(x => x. We'll also implement new entities, Order and OrderDetail , to track In this article, we have looked at how to dynamically build OR filters in an Entity Framework Core LINQ query by extending the LINQ Expression type with extension methods. A Quick Example. Like(c. Then I took exact generated SQL and executed in as SQL query in Visual Studio - took 100ms. Solution. Location. x, with more optimized SQL queries and the ability to include C#/VB. Every query consists of three main parts: Connection to the database via the ApplicationContext’s In this module, we will explore how to use Entity Framework Core to interact with databases through queries. Brand. I’ll use SQL Profiler to show the queries generated by LINQ. or to get all the customers from cities which start with vowels: With Split Queries, EF Core splits the related data retrieval into multiple more minor queries instead of a mega-query, reducing memory overhead and improving performance. This means you're offloading complexity to the database, Wrap-Up: Tag It Like a Pro. Here’s a classic scenario: Fetching blogs with their related posts. For queries that include related data, EF Core can split the query into multiple SQL statements to avoid cartesian explosion. Today, we’re going to take a closer look at subqueries in ASP. The Entity Framework Core Fluent API HasQueryFilter method is used to apply a global query filter to a specific entity, so that the filter is included in all query statements generated for the entity by EF Core. ; EF Core 7. MoveNext() is first called). x. This section details some common In-depth information on the more complex LINQ query operators when using Entity Framework Core In more recent versions of EF Core, and now in . And query is we are using ef core 3. For EF Core 5 there will be built-in method ToQueryString() used on IQueryable<>. Write the Entity Framework code-first model in C# along with your LINQ queries. Most queries (plain, simple, without date ranges . Whether you’re profiling queries, diagnosing issues, or optimizing performance, these little comments can save you hours of frustration and make you look like a debugging superhero. ToLi How To Use EF Core Query Filters. Before EF Core 7. Any() which spans 2 properties. Here’s the query flow when you execute a query: First, you execute a query: context. NET functions into LINQ-to-Entities queries. In this article we’ll explore how we can execute raw SQL queries in EF Core. Now, let’s use projection to select the field: Nested collections are usually either a) not supported or b) end up in horrible SELECT N+1 queries. For EF Core 3. You must specify an ILoggerFactory and you must specify a filter. I currently have working a search that checks each criteria, and if it is not blank it adds it to the query. Advanced EF Core queries are a powerful tool for any developer looking to optimize their data access performance. However, EF Core also provides mechanisms for executing raw SQL queries directly against the database in circumstances where you cannot use LINQ to represent the query (e. " – EF Core supports queries that include historical data through several specialized query operators: TemporalAsOf: Returns rows that were active (current) at the given UTC time. Query<T>(). StatusCode }). 2 EF Core 2. Applies to. Getting Started with Entity Framework Core and SQL Server Your use case of an external database can still be achieved using EF Core, there is no need to resort to ADO. To batch multiple queries, simply append Future or FutureValue method to the query. The FromSql method in Entity Framework Core allows you to execute a raw SQL query and map the results to entities. x as well as in Entity Framework Core. FromSql() method to execute raw SQL queries for the underlying database and get the results as entity objects. Contains(p. 1 And we want to use dynamic query filter, I tried sample implementation but did not work correctly we expected, filtering always same tenant id,i tried to explain at below. SelectMany in Entity Framework Core is an operator that flattens out the collection of collections into one single collection of objects. I'm trying learn to write efficient Entity Framework queries when data has to be fetched based on multiple joins, including a many-to-many via a junction table. NET 6 with EF Core. I'm developing an application (. 1, C# 8) that is using Entity Framework Core. Functions. Take(5 This method signals to EF Core that it should split queries, enabling data retrieval optimization: var companies = _dbContext. This is a single row from the current table or history table for a given primary key. There are only a couple of small tricks. Entity Framework Core emits SQL via the logging system. No more handcrafting SQL for every little query. If you're using EF Core 2. EF Core supports mapping JSON columns to . 1: return contextGeneric. [Name] FROM [Products] AS [p] If you want to add a hint such as NOLOCK to this query, there is currently no easy way through EF Core. [ProductID], [p]. We discussed what it is, and when we might use it, and created an example implementation for soft deleting entities. 1 and trying to build a query using Exists by means of . Utilizing the First-Level Cache with Find. It's used to retrieve data from a database using custom SQL and map it directly to a type that represents the data. (Note that some functions and namespaces changed for EF Core 3, so and remain in . ProdID)) // Enumerable. The DbQuery maps to a Handling Complex Query Scenarios with Entity Framework Core. Any() allows the execution of nested filter conditions without blowing up the expression tree. The LINQ interface provides a common abstraction for constructing Before diving into optimization techniques, it's essential to understand how EF Core processes queries: LINQ Query Definition: you define queries using LINQ. The method you have created iterates over an IQueryable<> object that's created by EF. 2+) if you’re capturing queries in logs consider using the TagWith feature to output an arbitrary Continue reading Labelling Entity Conclusion: Elevate Your EF Core Queries. A common way to implement pagination with databases is to use the Skip and Take LINQ operators (OFFSET and LIMIT in SQL). Q: Can I use raw SQL queries with EF Core? A: Yes, you can use raw SQL queries with EF Core using the FromSqlRaw The merge options set for the query at the time of the compilation cannot be changed later. Translation to SQL: EF Core translates LINQ queries into For people using EF Core 5, your query will have a Query property and also a ToQueryString() method that can be called to retrieve the query string. 1 The definition of the entity is as follows: public class PublishSource { [Key] [DatabaseGenerated(DatabaseGeneratedOption. The following example demonstrates executing a raw SQL query to MS SQL Server database. By leveraging raw SQL queries, LINQ queries, and other advanced techniques, you can write more efficient and performant queries. ToList(); As a result, EF Core will TIP This use of aggregates is very similar to the way JSON documents are mapped when using the EF Core provider for Azure Cosmos DB. For This query generates the following SQL: SELECT [p]. Contains extension EF Core uses the LINQ syntax as a domain-specific language (DSL) within C# codebases as a starting point for translating your queries into SQL. This has a quasi relationship via attributes. Online C# and LINQ playground. Compiled Queries are more performant than Like query supports wildcard characters and hence very useful compared to the string extension methods in some scenarios. In EF Core, compiled queries are implemented using the CompileQuery() or CompileQueryAsync() method. Net, this solution is based on this generic solution for EF Core by @ErikEj. Introduction to EF Core Where In. ToListAsync(); // Your debug console in Visual Studio should contain all the information you need Entity Framework configuration. Major ORM like NHibernate had this feature for a long time but, unfortunately for Entity Framework Core users, second level caching is only available through third party libraries. The IQueryable<> variable has deferred execution, therefore internally, EF will only make the call to the database when the IQueryable<> is iterated over (i. NET Core EF tutorial lists Select as an option, as I was asked to help develop that tutorial . In EF Core 5. Now, we can start querying data from the database by using the EF Core. 0, the Include method now supports filtering of the entities included. However, depending on its placement in the LINQ query, it may cause EF Core to disregard the OrderBy clause because Distinct forces the query to focus on eliminating duplicates before applying ordering. If you have queries that you execute frequently in your application with a different set of parameters, it can be helpful to explicitly compile the query and reuse it throughout the lifetime of your application. EF Core also provides the SqlQuery method that can execute raw SQL queries that return scalar or non-entity types. // Then when executing the query with var results = query. NET feature, there are some limitations to be aware of when it this does not seem to happen anymore in . The JSON documents shown above are very simple, but this mapping capability can also be Key Improvements. In this post I will explore the performance EF Core and EF 6 in how they handle of the FirstOrDefault() EF query. Here is an example of Q: How can I optimize query performance in EF Core? A: You can optimize query performance by using AsNoTracking for read-only queries, leveraging AsSplitQuery to split large queries, and indexing your database tables appropriately. Such raw SQL queries can return entity types or query types (from EF Core 2. Category has ID, Name, Parent and Children. when . Let’s dive in 1. If the result contains the same entity multiple times, you get back same instance for each occurrence. 0, it was sometimes necessary to use the ExecuteSql APIs to perform a "bulk update" on the database, as above; this is considerably more efficient than querying for all matching rows and then using SaveChanges to modify them. i don't know when it changed in . 1 see the @Thom Kiesewetter's answer. The SQL IN operator allows you to check if a value matches a list of values. So, are you ready to take your EF Core This is part 1 of a multi-part series on benchmarking EF Core 6 and EF6 using BenchmarkDotNet. Companies . SqlQuery. Once the query is compiled, you can only supply parameters of primitive type but you cannot replace parts of the query that would change the generated SQL. Today, we're going to tackle a beast of a topic: advanced EF Core query optimization. In Entity Framework (EF) Core, JSON columns can be used to store and query JSON data in a database. Visit the We will explore how to work with LINQ (Language Integrated Query) in C# for querying data efficiently. When you’ve created tables that are related, you’ll often need to get data from both tables at once, or filter records from one table based on values in another table. I find that allowing the compiled queries to be in the DBContext and using the AddDbContextPool EF Core supports the views, here is the details. SQL does not support tree like results so you run into the object-relational impedance mismatch and it hurts. If you want fast and effective queries then think about using Entity Framework Core provides the DbSet. People. e. Warning. Source Code: The source code of this project available in GitHub. Caching entities or query results to improve an application's performance is a very frequent scenario. To Regarding Entity Framework Core, there are many rules, today I will present you 5 basic ones that should be followed when writing queries. Item has a Category. In the following example, I'd like to Query many-to-many related data using Entity Framework Core. However, the Query Hint feature allows you to do it easily by changing the LINQ to: To help with this difficulty, you may want to use EF's query tags feature, which allows you to inject a small, identifying comment into the SQL query: var myLocation = new Point(1, 2); var nearestPeople = await (from f in context. Note: Entity Framework Core Plus Query Cache Description. 0 contains provider-agnostic support for JSON columns, with an implementation for SQL Server. Needed to get user, with related current password record, Entity Framework Core uses Language Integrate Query (LINQ) to query data from the database. And PwdHistory(int id, int UserId, user User). This filter makes sure that we don't get any additional rows for base types or sibling types not in the result. ToPageAsync is currently annotated as experimental, since it may be replaced with a more generic EF pagination API that isn't Azure Cosmos DB specific. Once this delegate is acquired, it can be invoked directly to execute the query, without providing the LINQ expression tree. Collaborate with us on GitHub. I am working with EF CORE 2. Products . Fortunately there is a small extension for EF now (for both EF6 and EF Core) which you could try. See Using EF. But the ASP. TemporalAll: Returns all rows in the historical data. A DbQuery is a property on the DbContext that acts similarly to a DbSet, providing a root for LINQ queries. So, we can use LINQ for querying against DbSet, which will be converted to an SQL query Back in October, I did a post on Entity Framework Core: Logging which covers enabling logging for Entity Framework Core. Departments) . Could be many or none. Database: The Database for this tutorial is taken from the chinook database. Without Split Queries (Single Query) Interesting case and it worked!! If you have table/model user(int id, int? passwordId, ICollection<PwdHist> passwordHistoryCollection) where collection is history of passwords. Querying efficiently is a vast subject, that covers subjects as wide-ranging as indexes, related entity loading strategies, and many others. Excerpt from Features not in EF Core (note the word not ) and Roadmap : The interactive playground will run the code for you and show what SQL will be generated when using Entity Framework. While FromSql is useful for querying entities defined in your model, SqlQuery allows you to easily query for scalar, non-entity types via SQL, without needing to drop down to lower-level data access APIs. Here is an example from this EF supports compiled queries, which allow the explicit compilation of a LINQ query into a . var sql = _context. This article presents a discussion on how we can work with raw SQL queries in Entity Framework Core. You can execute queries using LINQ or by writing raw SQL. In my demos and testing, I will create the compiled queries in the code close to the execution and my favorite location: in the DBContext class. Querying in Entity Framework Core remains the same as in EF 6 to load entities from the database. I created a function which accepts 3 parameters, inside that function I am executing a LINQ (lambda expression query), returning a list. along with query types. The source for this content can be found on GitHub, where you can also create and review issues and pull requests. DbSet. Note that these property/method only apply to a query, not the result - often there is no interim query variable as they're run immediately, so it is easiest to split a query that is formed and run into two steps to Entity Framework Core is an ORM (Object Relational Mapper) that allows us to leverage LINQ (Language Integrated Query) to abstract away the SQL (Structured Query Language) that would otherwise need to be written for interactions with a database. I'm getting the filter conditions in JSON and DbSet. More details in this issue Now the query does make sense to me (I've asked to include children and I've got them!), but can imagine that I would like to have the where clause applied to the child collection in some scenarios. Departments. Identity)] public int Id { get; set; } [Required] public string Name { get; set; } [Required] public Dictionary<string, string> Linq-to-Entities Query. 0. Always validate user input: While EF Core protects against SQL injection attacks by using parameters and escaping literals in queries, it does not validate inputs. For ex: If we were to search all the 4 lettered names with 'ri' as the middle characters we could do EF. Brandid) . EF Core uses LINQ to query data from the database. Filtering with EF Core through multiple nested object relationships. it's more consistent with SQL now EF Core 会自动将此类筛选器应用于涉及这些实体类型的任何 LINQ 查询。 EF Core 还将其应用于使用 Include 或导航属性进行间接引用的实体类型。 此功能的一些常见应用如下： 软删除 - 实体类型定义 IsDeleted 属性。 多租户 - 实体类型定义 TenantId 属性。 示例 var query = _context. MemoryJoin (name might be confusing, but it supports both EF6 and EF Core). In this log output, EF Core executed a database query to retrieve the entity with an ID of 1. That’s where FromSql swoops in to save the day. Contains extension method on an array in your Where expression. What you ask EF to do is to return an object tree. As stated in author's article it modifies SQL query passed to server and injects VALUES construction with data from your local list. Array and JSON Utilization: By transforming the range data into an array, EF Core can execute the query using native SQL capabilities more efficiently. The [Keyless] Data Annotation became available in EFCore 5. Use Projections. NET types EF Core – SELECT queries involving multiple tables. However, while LINQ is an awesome . However, it contributes most to the performance of any I am creating an application that searches the database and allows the user to dynamically add any criteria (around 50 possible), much like the following SO question: Creating dynamic queries with entity framework. I have an Item. 1 : How to do sub query in Select. Mastering EF Core queries is a journey, and by following these best practices, you can significantly improve the performance and efficiency of your applications. 1 an We're using EFCore 3. FromSql(query, Understanding Queries in Entity Framework Core. See: Store a Dictionary as a JSON string using EF Core 2. Id, sh. NET Core Entity Framework The DbQuery type was introduced in EF Core 2. Net 5+ the following subtle change need to be applied: Core 2. 0. 1 Release Candidate 1 available since 7 may 2018, you can take advantage of the proposed new feature which is query types:. And now we're getting support for querying unmapped types with raw SQL In this article, I’ll show examples of how to execute basic SELECT queries when using EF Core. 0/Sql server). Azure Cosmos DB does not support backwards pagination, and does not provide a count of the total pages or items. Use Logging with Entity Framework Core 3. Entity Framework 4. I would like to filter a table with several filtering options. For more information, see EF Merge Options and Compiled Queries. Where(p => ids. The following code in a . 0 introduced ExecuteUpdate and ExecuteDelete, which made it possible to express efficient bulk So, you’ve embraced Entity Framework Core, and life’s been good. Factory. Both LINQ (Language Integrated Query) and LINQ-to-Objects are supported when querying data. Here, you will learn how to write LINQ-to-Entities queries and get the result in Entity Framework 6. The DbSet class is derived from IQuerayable. EF7 introduced support for returning scalar types using SQL queries. All future queries will be stored in a pending list, and when the first future query requires a database round trip, all queries will be resolved in the same SQL EF Core 7. This reduces the amount of data transferred from the database to the application. var selectionCriteria = someHugeList. It doesn't make any sense to me. public async Task<List<Product>> GetProducts(params int[] ids) { return await context. Union(_context. I use EF Core for a long time and it seem to perform reasonably. This feature was added in EF Core 2. Include(company => company. It is a very useful operator with many use cases. Note. FunctionReturnVarchar({0});", id Summary: in this tutorial, you will learn how to use EF Core WHERE IN to check whether a value matches a list of values. Single WHERE Clause with Any: The use of . Brandfactory. FromSql. If you're using EF 6. You’ll gain hands-on experience in using LINQ, applying filters, and Querying in Entity Framework Core remains the same as in EF 6. Net core console application (EF core 2. EF Core Query flow. NET types to JSON documents. In this article, I’ll show examples of executing queries like this where more than one As per the comments on the question, the way you do this in EF Core is the same as for LINQ-to-SQL: use the Enumerable. The FromSql method is an extension method on the DbSet class and takes a raw SQL query string and an Welcome to another deep dive into the world of Entity Framework Core (EF Core). Add. Appropriate validation, per the application's requirements, should be performed before values from un-trusted sources are used in LINQ queries, assigned to entity properties, or passed to In this week's newsletter I want to introduce you to an interesting feature in EF Core called Compiled Queries. Factorycode)) . It is working not that much different than normal entities; but has some special points. Offset pagination. [Description], [p]. We started by setting up the environment and the Database queries can be a bit like solving a puzzle, and one powerful tool in your toolkit is subqueries. Select(sh => new { sh. 0 the concept was renamed to keyless entity types. Parent and Children are of Category too. This technique bypasses the cache lookup, and provides the most optimized way to execute a query in EF Core. Name, "_ri_");. ToList Code language: CSS (css) Second, EF Core reads model (Department class), works with the data provider (SQL Server in this example) to construct a corresponding SQL statement: I'm trying to convert some common queries that we use to an API call using EF Core but I can't seem to get it working. But it doesn't bring the full category, with its parent and children. g. The SQL that will typically be run will looking something like this: select * Skip to main content Entity Framework sub query. Remember, the key to mastering advanced EF Core queries is to experiment and iterate. When materializing an entity, EF Core will return the same entity instance from the change tracker if it's already being tracked. a Full-Text Search), if the generated SQL is not efficient enough, if you want to make use of existing stored procedures, or if you just prefer to write your queries in SQL Labelling Entity Framework Core queries in log files using TagWith In Entity Framework Core (2. In this article, we explored EF Core’s global query filter feature. However, it doesn't enable operations that write to the database e. In EF Core 3. Visit LINQ Tutorials to learn LINQ step by step. Remember, the key is to understand your data needs and choose the right approach for each scenario. JSON columns bring the capabilities of using EF Core against document databases to documents embedded in a relational database. Be on the lookout for future EF Core vs EF6 Benchmarking posts as we expand our benchmarking horizons. Here's a quick refresher on Query filters: Configure Writing paginating queries in Entity Framework Core. public class TestDbContext : DbContext { public DbSet<TenantUser> TenantUsers { get; set; } private readonly ITenantProvider _tenantProvider; private The query I pasted is the real query EF Core sends. Net Core 3. When I do a LINQ to Entities query for a specific Item, it doesn't return the related Category, unless I use the Include("Category") method. I advise you to fetch the nested collection data as a second, completely separate query. TagWith("This is my spatial query!") orderby f. Instead of retrieving entire entities, we must select only the necessary fields. It is EntityFrameworkCore. Entity Framework subquery. The code fragment I pasted first is executed in 3200ms. Although using the current API will generate a compilation warning (EF9102), doing The Select query isn’t obvious – in fact the EF Core documentation on loading relationships doesn’t even list it even though you can load relationships in a Select method. It also contains the script of the database For more detailed information on querying data with EF Core, visit our article Database Queries in Entity Framework Core. 1). But what happens when EF Core’s LINQ magic isn’t entirely cutting it? Maybe you need something specific, like a stored procedure or a complex SQL query that LINQ doesn’t handle elegantly. FromSql("select dbo. This behavior can feel like a bug, but it is better understood as a EF+ Query Future opens up all batching future queries features for Entity Framework Core users. Finally, we discussed other important considerations when using global query filters and how to mitigate potential issues. One possible solution is to use 3rd party library, like NeinLinq. i'm guessing that's the reason the other answers look like bugs. Given a page size of 10 results, the third page can be fetched with EF Core as follows: Seems someone has been struggling with that and found solution. The database is an integral part of every application. 0 and 3. If you want an in-depth dive into Query filters, take a look at the newsletter issue where I talked about using query filters with EF Core. . Distance(myLocation) descending select f). This support allows the mapping of aggregates built from . AsSplitQuery() . LINQ allows you to use C# (or your . NET Core, because i previously used LINQ-to-SQL in NET Framework 4. 8. 1 under the name of query types. This is typically many rows Note. Written by Ali Hamza Ansari, February 25, 2025. NET delegate. Factoryid)); Please also remember that EF core don't evaluate yet Union on database site, it will be evaluated locally. Query Tags are the sticky notes of EF Core—simple, effective, and a lifesaver when debugging complex systems. Write code in the browser. By default, EF Core generates a single SQL query with JOINs to Entity Framework Core を使用すると、リレーショナル データベースを操作するときに SQL クエリにドロップ ダウンすることができます。 必要なクエリを LINQ を使用して表現できない場合、または LINQ クエリを実行すると EF で非効率的な SQL が生成される場合に、SQL クエリは役立ちます。 This answer is for EF Core 2. Additionally, if you have ever hand-rolled a database call using SqlDataReader, you'll When querying for derived entities, which use the TPH pattern, EF Core adds a predicate over discriminator column in the query. This post is going to expand on that previous post and show you how to get the parameter values used in the queries in addition to the SQL statements being used. Since a tracking query uses the change tracker, EF Core will do identity resolution in a tracking query. dsjwhnyerlqvewnwqzmalqqykfxrkruoaqgbrxqpxygqznrjsvfsxqlzeewsemaewypxtrfzqorenfppxs
Ef core query 01/26/2025 04/08/2021 by Mak. The most common use cases for this feature include properties that indicate that an entity instance is deleted, or not otherwise active, and a tenant identifier in an application that I need some sample code for my project. EntityFrameworkCore: "NeinLinq extends LINQ providers such as Entity Framework to enable reusing functions, rewriting queries, and building dynamic queries using translatable predicates and selectors. 10. Property in EF Core queries for more information and examples. 1. Set<string>() . Since EF 7 is renamed to Entity Framework Core I EF Core has a concept of mixed client/database evaluation in LINQ queries which allows them to release EF Core versions with incomplete/very inefficient query processing like in your case. Net 5+ but the same generic concept can still be applied) The Distinct operator instructs EF Core to select unique records. In addition to entity types, an EF Core model can contain query types, which can be used to carry out database queries against data that isn't mapped to entity types. NET language of choice) to write strongly typed queries based on your derived context and entity classes. 1. If you're like me, you've probably spent countless EF Core is getting many new and exciting features in the upcoming version. Custom methods for obvious reasons cannot be translated to SQL. Select(x => x. We'll also implement new entities, Order and OrderDetail , to track In this article, we have looked at how to dynamically build OR filters in an Entity Framework Core LINQ query by extending the LINQ Expression type with extension methods. A Quick Example. Like(c. Then I took exact generated SQL and executed in as SQL query in Visual Studio - took 100ms. Solution. Location. x, with more optimized SQL queries and the ability to include C#/VB. Every query consists of three main parts: Connection to the database via the ApplicationContext’s In this module, we will explore how to use Entity Framework Core to interact with databases through queries. Brand. I’ll use SQL Profiler to show the queries generated by LINQ. or to get all the customers from cities which start with vowels: With Split Queries, EF Core splits the related data retrieval into multiple more minor queries instead of a mega-query, reducing memory overhead and improving performance. This means you're offloading complexity to the database, Wrap-Up: Tag It Like a Pro. Here’s a classic scenario: Fetching blogs with their related posts. For queries that include related data, EF Core can split the query into multiple SQL statements to avoid cartesian explosion. Today, we’re going to take a closer look at subqueries in ASP. The Entity Framework Core Fluent API HasQueryFilter method is used to apply a global query filter to a specific entity, so that the filter is included in all query statements generated for the entity by EF Core. ; EF Core 7. MoveNext() is first called). x. This section details some common In-depth information on the more complex LINQ query operators when using Entity Framework Core In more recent versions of EF Core, and now in . And query is we are using ef core 3. For EF Core 5 there will be built-in method ToQueryString() used on IQueryable<>. Write the Entity Framework code-first model in C# along with your LINQ queries. Most queries (plain, simple, without date ranges . Whether you’re profiling queries, diagnosing issues, or optimizing performance, these little comments can save you hours of frustration and make you look like a debugging superhero. ToLi How To Use EF Core Query Filters. Before EF Core 7. Any() which spans 2 properties. Here’s the query flow when you execute a query: First, you execute a query: context. NET functions into LINQ-to-Entities queries. In this article we’ll explore how we can execute raw SQL queries in EF Core. Now, let’s use projection to select the field: Nested collections are usually either a) not supported or b) end up in horrible SELECT N+1 queries. For EF Core 3. You must specify an ILoggerFactory and you must specify a filter. I currently have working a search that checks each criteria, and if it is not blank it adds it to the query. Advanced EF Core queries are a powerful tool for any developer looking to optimize their data access performance. However, EF Core also provides mechanisms for executing raw SQL queries directly against the database in circumstances where you cannot use LINQ to represent the query (e. " – EF Core supports queries that include historical data through several specialized query operators: TemporalAsOf: Returns rows that were active (current) at the given UTC time. Query<T>(). StatusCode }). 2 EF Core 2. Applies to. Getting Started with Entity Framework Core and SQL Server Your use case of an external database can still be achieved using EF Core, there is no need to resort to ADO. To batch multiple queries, simply append Future or FutureValue method to the query. The FromSql method in Entity Framework Core allows you to execute a raw SQL query and map the results to entities. x as well as in Entity Framework Core. FromSql() method to execute raw SQL queries for the underlying database and get the results as entity objects. Contains(p. 1 And we want to use dynamic query filter, I tried sample implementation but did not work correctly we expected, filtering always same tenant id,i tried to explain at below. SelectMany in Entity Framework Core is an operator that flattens out the collection of collections into one single collection of objects. I'm trying learn to write efficient Entity Framework queries when data has to be fetched based on multiple joins, including a many-to-many via a junction table. NET 6 with EF Core. I'm developing an application (. 1, C# 8) that is using Entity Framework Core. Functions. Take(5 This method signals to EF Core that it should split queries, enabling data retrieval optimization: var companies = _dbContext. This is a single row from the current table or history table for a given primary key. There are only a couple of small tricks. Entity Framework Core emits SQL via the logging system. No more handcrafting SQL for every little query. If you're using EF Core 2. EF Core supports mapping JSON columns to . 1: return contextGeneric. [Name] FROM [Products] AS [p] If you want to add a hint such as NOLOCK to this query, there is currently no easy way through EF Core. [ProductID], [p]. We discussed what it is, and when we might use it, and created an example implementation for soft deleting entities. 1 and trying to build a query using Exists by means of . Utilizing the First-Level Cache with Find. It's used to retrieve data from a database using custom SQL and map it directly to a type that represents the data. (Note that some functions and namespaces changed for EF Core 3, so and remain in . ProdID)) // Enumerable. The DbQuery maps to a Handling Complex Query Scenarios with Entity Framework Core. Any() allows the execution of nested filter conditions without blowing up the expression tree. The LINQ interface provides a common abstraction for constructing Before diving into optimization techniques, it's essential to understand how EF Core processes queries: LINQ Query Definition: you define queries using LINQ. The method you have created iterates over an IQueryable<> object that's created by EF. 2+) if you’re capturing queries in logs consider using the TagWith feature to output an arbitrary Continue reading Labelling Entity Conclusion: Elevate Your EF Core Queries. A common way to implement pagination with databases is to use the Skip and Take LINQ operators (OFFSET and LIMIT in SQL). Q: Can I use raw SQL queries with EF Core? A: Yes, you can use raw SQL queries with EF Core using the FromSqlRaw The merge options set for the query at the time of the compilation cannot be changed later. Translation to SQL: EF Core translates LINQ queries into For people using EF Core 5, your query will have a Query property and also a ToQueryString() method that can be called to retrieve the query string. 1 The definition of the entity is as follows: public class PublishSource { [Key] [DatabaseGenerated(DatabaseGeneratedOption. The following example demonstrates executing a raw SQL query to MS SQL Server database. By leveraging raw SQL queries, LINQ queries, and other advanced techniques, you can write more efficient and performant queries. ToList(); As a result, EF Core will TIP This use of aggregates is very similar to the way JSON documents are mapped when using the EF Core provider for Azure Cosmos DB. For This query generates the following SQL: SELECT [p]. Contains extension EF Core uses the LINQ syntax as a domain-specific language (DSL) within C# codebases as a starting point for translating your queries into SQL. This has a quasi relationship via attributes. Online C# and LINQ playground. Compiled Queries are more performant than Like query supports wildcard characters and hence very useful compared to the string extension methods in some scenarios. In EF Core, compiled queries are implemented using the CompileQuery() or CompileQueryAsync() method. Net, this solution is based on this generic solution for EF Core by @ErikEj. Introduction to EF Core Where In. ToListAsync(); // Your debug console in Visual Studio should contain all the information you need Entity Framework configuration. Major ORM like NHibernate had this feature for a long time but, unfortunately for Entity Framework Core users, second level caching is only available through third party libraries. The IQueryable<> variable has deferred execution, therefore internally, EF will only make the call to the database when the IQueryable<> is iterated over (i. NET Core EF tutorial lists Select as an option, as I was asked to help develop that tutorial . In EF Core 5. Now, we can start querying data from the database by using the EF Core. 0, the Include method now supports filtering of the entities included. However, depending on its placement in the LINQ query, it may cause EF Core to disregard the OrderBy clause because Distinct forces the query to focus on eliminating duplicates before applying ordering. If you have queries that you execute frequently in your application with a different set of parameters, it can be helpful to explicitly compile the query and reuse it throughout the lifetime of your application. EF Core also provides the SqlQuery method that can execute raw SQL queries that return scalar or non-entity types. // Then when executing the query with var results = query. NET feature, there are some limitations to be aware of when it this does not seem to happen anymore in . The JSON documents shown above are very simple, but this mapping capability can also be Key Improvements. In this post I will explore the performance EF Core and EF 6 in how they handle of the FirstOrDefault() EF query. Here is an example of Q: How can I optimize query performance in EF Core? A: You can optimize query performance by using AsNoTracking for read-only queries, leveraging AsSplitQuery to split large queries, and indexing your database tables appropriately. Such raw SQL queries can return entity types or query types (from EF Core 2. Category has ID, Name, Parent and Children. when . Let’s dive in 1. If the result contains the same entity multiple times, you get back same instance for each occurrence. 0, it was sometimes necessary to use the ExecuteSql APIs to perform a "bulk update" on the database, as above; this is considerably more efficient than querying for all matching rows and then using SaveChanges to modify them. i don't know when it changed in . 1 see the @Thom Kiesewetter's answer. The SQL IN operator allows you to check if a value matches a list of values. So, are you ready to take your EF Core This is part 1 of a multi-part series on benchmarking EF Core 6 and EF6 using BenchmarkDotNet. Companies . SqlQuery. Once the query is compiled, you can only supply parameters of primitive type but you cannot replace parts of the query that would change the generated SQL. Today, we're going to tackle a beast of a topic: advanced EF Core query optimization. In Entity Framework (EF) Core, JSON columns can be used to store and query JSON data in a database. Visit the We will explore how to work with LINQ (Language Integrated Query) in C# for querying data efficiently. When you’ve created tables that are related, you’ll often need to get data from both tables at once, or filter records from one table based on values in another table. I find that allowing the compiled queries to be in the DBContext and using the AddDbContextPool EF Core supports the views, here is the details. SQL does not support tree like results so you run into the object-relational impedance mismatch and it hurts. If you want fast and effective queries then think about using Entity Framework Core provides the DbSet. People. e. Warning. Source Code: The source code of this project available in GitHub. Caching entities or query results to improve an application's performance is a very frequent scenario. To Regarding Entity Framework Core, there are many rules, today I will present you 5 basic ones that should be followed when writing queries. Item has a Category. In the following example, I'd like to Query many-to-many related data using Entity Framework Core. However, the Query Hint feature allows you to do it easily by changing the LINQ to: To help with this difficulty, you may want to use EF's query tags feature, which allows you to inject a small, identifying comment into the SQL query: var myLocation = new Point(1, 2); var nearestPeople = await (from f in context. Note: Entity Framework Core Plus Query Cache Description. 0 contains provider-agnostic support for JSON columns, with an implementation for SQL Server. Needed to get user, with related current password record, Entity Framework Core uses Language Integrate Query (LINQ) to query data from the database. And PwdHistory(int id, int UserId, user User). This filter makes sure that we don't get any additional rows for base types or sibling types not in the result. ToPageAsync is currently annotated as experimental, since it may be replaced with a more generic EF pagination API that isn't Azure Cosmos DB specific. Once this delegate is acquired, it can be invoked directly to execute the query, without providing the LINQ expression tree. Collaborate with us on GitHub. I am working with EF CORE 2. Products . Fortunately there is a small extension for EF now (for both EF6 and EF Core) which you could try. See Using EF. But the ASP. TemporalAll: Returns all rows in the historical data. A DbQuery is a property on the DbContext that acts similarly to a DbSet, providing a root for LINQ queries. So, we can use LINQ for querying against DbSet, which will be converted to an SQL query Back in October, I did a post on Entity Framework Core: Logging which covers enabling logging for Entity Framework Core. Departments) . Could be many or none. Database: The Database for this tutorial is taken from the chinook database. Without Split Queries (Single Query) Interesting case and it worked!! If you have table/model user(int id, int? passwordId, ICollection<PwdHist> passwordHistoryCollection) where collection is history of passwords. Querying efficiently is a vast subject, that covers subjects as wide-ranging as indexes, related entity loading strategies, and many others. Excerpt from Features not in EF Core (note the word not ) and Roadmap : The interactive playground will run the code for you and show what SQL will be generated when using Entity Framework. While FromSql is useful for querying entities defined in your model, SqlQuery allows you to easily query for scalar, non-entity types via SQL, without needing to drop down to lower-level data access APIs. Here is an example from this EF supports compiled queries, which allow the explicit compilation of a LINQ query into a . var sql = _context. This article presents a discussion on how we can work with raw SQL queries in Entity Framework Core. You can execute queries using LINQ or by writing raw SQL. In my demos and testing, I will create the compiled queries in the code close to the execution and my favorite location: in the DBContext class. Querying in Entity Framework Core remains the same as in EF 6 to load entities from the database. I created a function which accepts 3 parameters, inside that function I am executing a LINQ (lambda expression query), returning a list. along with query types. The source for this content can be found on GitHub, where you can also create and review issues and pull requests. DbSet. Note that these property/method only apply to a query, not the result - often there is no interim query variable as they're run immediately, so it is easiest to split a query that is formed and run into two steps to Entity Framework Core is an ORM (Object Relational Mapper) that allows us to leverage LINQ (Language Integrated Query) to abstract away the SQL (Structured Query Language) that would otherwise need to be written for interactions with a database. I'm getting the filter conditions in JSON and DbSet. More details in this issue Now the query does make sense to me (I've asked to include children and I've got them!), but can imagine that I would like to have the where clause applied to the child collection in some scenarios. Departments. Identity)] public int Id { get; set; } [Required] public string Name { get; set; } [Required] public Dictionary<string, string> Linq-to-Entities Query. 0. Always validate user input: While EF Core protects against SQL injection attacks by using parameters and escaping literals in queries, it does not validate inputs. For ex: If we were to search all the 4 lettered names with 'ri' as the middle characters we could do EF. Brandid) . EF Core uses LINQ to query data from the database. Filtering with EF Core through multiple nested object relationships. it's more consistent with SQL now EF Core 会自动将此类筛选器应用于涉及这些实体类型的任何 LINQ 查询。 EF Core 还将其应用于使用 Include 或导航属性进行间接引用的实体类型。 此功能的一些常见应用如下： 软删除 - 实体类型定义 IsDeleted 属性。 多租户 - 实体类型定义 TenantId 属性。 示例 var query = _context. MemoryJoin (name might be confusing, but it supports both EF6 and EF Core). In this log output, EF Core executed a database query to retrieve the entity with an ID of 1. That’s where FromSql swoops in to save the day. Contains extension method on an array in your Where expression. What you ask EF to do is to return an object tree. As stated in author's article it modifies SQL query passed to server and injects VALUES construction with data from your local list. Array and JSON Utilization: By transforming the range data into an array, EF Core can execute the query using native SQL capabilities more efficiently. The [Keyless] Data Annotation became available in EFCore 5. Use Projections. NET types EF Core – SELECT queries involving multiple tables. However, while LINQ is an awesome . However, it contributes most to the performance of any I am creating an application that searches the database and allows the user to dynamically add any criteria (around 50 possible), much like the following SO question: Creating dynamic queries with entity framework. I have an Item. 1 : How to do sub query in Select. Mastering EF Core queries is a journey, and by following these best practices, you can significantly improve the performance and efficiency of your applications. 1 an We're using EFCore 3. FromSql(query, Understanding Queries in Entity Framework Core. See: Store a Dictionary as a JSON string using EF Core 2. Id, sh. NET Core Entity Framework The DbQuery type was introduced in EF Core 2. Net 5+ the following subtle change need to be applied: Core 2. 0. 1 Release Candidate 1 available since 7 may 2018, you can take advantage of the proposed new feature which is query types:. And now we're getting support for querying unmapped types with raw SQL In this article, I’ll show examples of how to execute basic SELECT queries when using EF Core. 0/Sql server). Azure Cosmos DB does not support backwards pagination, and does not provide a count of the total pages or items. Use Logging with Entity Framework Core 3. Entity Framework 4. I would like to filter a table with several filtering options. For more information, see EF Merge Options and Compiled Queries. Where(p => ids. The following code in a . 0 introduced ExecuteUpdate and ExecuteDelete, which made it possible to express efficient bulk So, you’ve embraced Entity Framework Core, and life’s been good. Factory. Both LINQ (Language Integrated Query) and LINQ-to-Objects are supported when querying data. Here, you will learn how to write LINQ-to-Entities queries and get the result in Entity Framework 6. The DbSet class is derived from IQuerayable. EF7 introduced support for returning scalar types using SQL queries. All future queries will be stored in a pending list, and when the first future query requires a database round trip, all queries will be resolved in the same SQL EF Core 7. This reduces the amount of data transferred from the database to the application. var selectionCriteria = someHugeList. It doesn't make any sense to me. public async Task<List<Product>> GetProducts(params int[] ids) { return await context. Union(_context. I use EF Core for a long time and it seem to perform reasonably. This feature was added in EF Core 2. Include(company => company. It is a very useful operator with many use cases. Note. FunctionReturnVarchar({0});", id Summary: in this tutorial, you will learn how to use EF Core WHERE IN to check whether a value matches a list of values. Single WHERE Clause with Any: The use of . Brandfactory. FromSql. If you're using EF 6. You’ll gain hands-on experience in using LINQ, applying filters, and Querying in Entity Framework Core remains the same as in EF 6. Net core console application (EF core 2. EF Core Query flow. NET types to JSON documents. In this article, I’ll show examples of executing queries like this where more than one As per the comments on the question, the way you do this in EF Core is the same as for LINQ-to-SQL: use the Enumerable. The FromSql method is an extension method on the DbSet class and takes a raw SQL query string and an Welcome to another deep dive into the world of Entity Framework Core (EF Core). Add. Appropriate validation, per the application's requirements, should be performed before values from un-trusted sources are used in LINQ queries, assigned to entity properties, or passed to In this week's newsletter I want to introduce you to an interesting feature in EF Core called Compiled Queries. Factorycode)) . It is working not that much different than normal entities; but has some special points. Offset pagination. [Description], [p]. We started by setting up the environment and the Database queries can be a bit like solving a puzzle, and one powerful tool in your toolkit is subqueries. Select(sh => new { sh. 0 the concept was renamed to keyless entity types. Parent and Children are of Category too. This technique bypasses the cache lookup, and provides the most optimized way to execute a query in EF Core. Name, "_ri_");. ToList Code language: CSS (css) Second, EF Core reads model (Department class), works with the data provider (SQL Server in this example) to construct a corresponding SQL statement: I'm trying to convert some common queries that we use to an API call using EF Core but I can't seem to get it working. But it doesn't bring the full category, with its parent and children. g. The SQL that will typically be run will looking something like this: select * Skip to main content Entity Framework sub query. Remember, the key to mastering advanced EF Core queries is to experiment and iterate. When materializing an entity, EF Core will return the same entity instance from the change tracker if it's already being tracked. a Full-Text Search), if the generated SQL is not efficient enough, if you want to make use of existing stored procedures, or if you just prefer to write your queries in SQL Labelling Entity Framework Core queries in log files using TagWith In Entity Framework Core (2. In this article, we explored EF Core’s global query filter feature. However, it doesn't enable operations that write to the database e. In EF Core 3. Visit LINQ Tutorials to learn LINQ step by step. Remember, the key is to understand your data needs and choose the right approach for each scenario. JSON columns bring the capabilities of using EF Core against document databases to documents embedded in a relational database. Be on the lookout for future EF Core vs EF6 Benchmarking posts as we expand our benchmarking horizons. Here's a quick refresher on Query filters: Configure Writing paginating queries in Entity Framework Core. public class TestDbContext : DbContext { public DbSet<TenantUser> TenantUsers { get; set; } private readonly ITenantProvider _tenantProvider; private The query I pasted is the real query EF Core sends. Net Core 3. When I do a LINQ to Entities query for a specific Item, it doesn't return the related Category, unless I use the Include("Category") method. I advise you to fetch the nested collection data as a second, completely separate query. TagWith("This is my spatial query!") orderby f. Instead of retrieving entire entities, we must select only the necessary fields. It is EntityFrameworkCore. Entity Framework subquery. The code fragment I pasted first is executed in 3200ms. Although using the current API will generate a compilation warning (EF9102), doing The Select query isn’t obvious – in fact the EF Core documentation on loading relationships doesn’t even list it even though you can load relationships in a Select method. It also contains the script of the database For more detailed information on querying data with EF Core, visit our article Database Queries in Entity Framework Core. 1). But what happens when EF Core’s LINQ magic isn’t entirely cutting it? Maybe you need something specific, like a stored procedure or a complex SQL query that LINQ doesn’t handle elegantly. FromSql("select dbo. This behavior can feel like a bug, but it is better understood as a EF+ Query Future opens up all batching future queries features for Entity Framework Core users. Finally, we discussed other important considerations when using global query filters and how to mitigate potential issues. One possible solution is to use 3rd party library, like NeinLinq. i'm guessing that's the reason the other answers look like bugs. Given a page size of 10 results, the third page can be fetched with EF Core as follows: Seems someone has been struggling with that and found solution. The database is an integral part of every application. 0 and 3. If you want an in-depth dive into Query filters, take a look at the newsletter issue where I talked about using query filters with EF Core. . Distance(myLocation) descending select f). This support allows the mapping of aggregates built from . AsSplitQuery() . LINQ allows you to use C# (or your . NET Core, because i previously used LINQ-to-SQL in NET Framework 4. 8. 1 under the name of query types. This is typically many rows Note. Written by Ali Hamza Ansari, February 25, 2025. NET delegate. Factoryid)); Please also remember that EF core don't evaluate yet Union on database site, it will be evaluated locally. Query Tags are the sticky notes of EF Core—simple, effective, and a lifesaver when debugging complex systems. Write code in the browser. By default, EF Core generates a single SQL query with JOINs to Entity Framework Core を使用すると、リレーショナル データベースを操作するときに SQL クエリにドロップ ダウンすることができます。 必要なクエリを LINQ を使用して表現できない場合、または LINQ クエリを実行すると EF で非効率的な SQL が生成される場合に、SQL クエリは役立ちます。 This answer is for EF Core 2. Additionally, if you have ever hand-rolled a database call using SqlDataReader, you'll When querying for derived entities, which use the TPH pattern, EF Core adds a predicate over discriminator column in the query. This post is going to expand on that previous post and show you how to get the parameter values used in the queries in addition to the SQL statements being used. Since a tracking query uses the change tracker, EF Core will do identity resolution in a tracking query. dsjwhn yerl qvewn wqzmalq qyk fxrkruoa qgbrxqp xygq znrjs vfsx qlze ewsema ewypx trfzqor enfppxs