An object-relational mapper (ORM) is an essential part of any project that includes a database. It simplifies the maintenance and processing of data, allowing developers to focus on code. But each ORM framework has its pitfalls that you have to be aware of before implementing it.


In this article, one of our Apriorit experts discusses key issues we faced with Entity Framework in one of our .NET projects. He explains how to speed up materialization and SELECT, INSERT, UPDATE, and DELETE statements in Entity. This article will be useful for developers who are looking for a library for their .NET projects or who are already working with Entity Framework.

What is an ORM?

An object-relational mapper (ORM) is software responsible for mapping between databases and object-oriented programming languages. An ORM creates a virtual database scheme and allows a developer to manipulate data at the object level. A mapping shows how an object and its properties are associated with data in database tables. The ORM uses this information to manage the transformation of data between databases and objects.

Using an ORM saves a developer a lot of time because it:

  • Automates the processes of inserting, updating, and deleting data according to commands from an application
  • Creates SQL queries automatically
  • Simplifies updating, maintaining, and reusing code
  • Enforces a Model–View–Controller pattern to structure code

On the negative side, ORM frameworks aren’t easy to learn. If you’re working with an extensive database, processing queries and editing data can take some time. Also, an abstract database can be a trap for inexperienced developers. Without knowledge of database operations, they may write optimized statements that slow down the database.

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Entity Framework — a complex ORM library

Entity Framework is an ORM library that allows for working with databases using .NET objects. It was originally created in 2008 as a way to realize custom repository patterns (DbConnection, DbCommand, etc.) for ADO.NET. Entity Framework is mainly used by websites written in .NET.

Issues we’ve faced using Entity Framework

At Apriorit, we have developed and supported several complex .NET projects using Entity Framework. It’s an efficient tool for database management, but over the years we’ve identified several critical issues with this library:

  • Slow processing of SELECT statements
  • Poor data materialization
  • Slow INSERT/UPDATE query processing with large volumes of data
  • Issues with executing the DELETE statement

Let’s take a closer look at why these issues occur. In the third part of the article, I’ll talk about third-party libraries we’ve used to improve Entity Framework performance.

Slow SELECT statement processing

The Entity Framework API is built on Language Integrated Query (LINQ), with a very small difference between client code and the SQL-translated code executed by the DBMS. Because of this, it has difficulties with processing the SELECT statement. For example, there’s a common performance issue with SELECT N+1 queries.

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Third-party libraries for Entity Framework

Despite the issues we’ve discussed, Entity Framework is a very useful library for .NET projects. At Apriorit, we use third-party libraries to improve its performance.

Developers all over the world have created lots of additional libraries and workarounds for Entity Framework. We’ve chosen the Entity Framework.Utilities and RefactorThis.GraphDiff libraries for our projects because they’re easy and fast to implement. We’ve also examined the possibility of using NHibernate and Dapper. However, NHibernate looks overengineered because of the Hibernate Query Language and drivers, and Dapper doesn’t create SQL queries, and our projects have used a DBMS and SQL dialects.

Let’s see how to use Entity Framework.Utilities and RefactorThis.GraphDiff to speed up the performance of Entity Framework.


In this article, we’ve discussed what Entity Framework is and dived deep into common issues with materialization and SELECT, INSERT, UPDATE, and DELETE statements. These operations can significantly slow down work with Entity Framework, especially when dealing with an extensive database. We’ve also shown you a way to speed up this library using third-party libraries.