Deadlock in the Entity Framework(EF6) Issue Resolved – SQL Server Solution

Entity Framework applications can face SQL Server deadlocks when multiple processes try to read and update the same data at the same time. This usually happens in applications that use background jobs, Windows services, scheduled tasks, or long-running database transactions.

In one of our EF6 projects, a Windows service was updating data across multiple tables inside a transaction. At the same time, the website was trying to read the same data for display. Because SQL Server uses locks during transactions, the website started facing a deadlock error.

In this blog, we will explain why this deadlock happened, how READ UNCOMMITTED helped in this case, what risks come with this approach, and what other options developers should consider before applying it in production

How to prevent and resolve deadlock problems in SQL Server?

In this article, I will share how I solve the entity framework deadlock issue. Recently, I faced one common but big issue related to deadlock in the entity framework(EF6).

We are working on the entity framework as a data access layered project. Project-based on job scheduling using background services, having SQL server operations like add, update, delete, etc.

Using SQL server transaction of entity framework(EF) which updates data in more than 10 tables in a single transaction.

So, we are driving SQL server data from those database tables and showing it on a front-end website form.

Suppose, We want to display all the information from all the database tables.

When an SQL server transaction is running at that time, SQL uses the locking method at the table or row level.

Now at this point, we have encountered a deadlock issue in the entity framework and also found out the total permanent solutions for deadlock issues related to entity framework 6.

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What is a Deadlock in Entity Framework and SQL Server?

A deadlock occurs when two or more database operations wait for each other to release locks, preventing any from continuing. SQL Server detects this situation and chooses one transaction as the deadlock victim.

In Entity Framework applications, deadlocks can occur when one process updates data while another attempts to read or update the same rows or related tables.
This is common in applications where:

• Background services update records in batches.
• Web applications read data from the same tables.
• Multiple tables are updated inside one transaction.
• Queries run for too long.
• Indexes are missing or not useful.
• Different processes access tables in different orders.

Problem Statement: EF6 Website Reading Data While SQL Server Transaction Is Running

In this project, a Windows service was running SQL Server transactions through Entity Framework. The transaction was adding, updating, and deleting data across multiple tables.

At the same time, the ASP.NET MVC website was reading data from those tables and showing it on the frontend.
When the transaction was running, SQL Server placed locks on rows or tables.

Because the website was also trying to read the same data, the application started showing this deadlock error:

Transaction Procedure ID 57 was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction.

This means SQL Server found two operations waiting on each other and stopped one of them so the other could continue.

SQL server transaction is running in Windows service which locks the tables/rows and we are reading data from table to display on our website.

but deadlocks are a general problem with database applications using transactions, so we are getting the following deadlock error in a website.

• Error: Transaction (Process ID 57) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction.
• Deadlock issues with EF

Why This Deadlock Happens in EF6 Applications

This type of deadlock usually occurs when read and write operations compete for the same database resources.
Common causes include:

• Long-running transactions
• Multiple table updates inside one transaction
• Website queries reading locked rows
• Background services are updating the same records.
• Missing indexes that make queries scan more data
• Large result sets are loaded into memory.
• Different processes access tables in a different order
• No retry handling after SQL Server chooses a deadlock victim

In this case, the issue appeared because the website needed to read data while the Windows service transaction was still running.

Solution Used: READ UNCOMMITTED Isolation Level in EF6

To reduce blocking for website read operations, we used the READ UNCOMMITTED isolation level for read-only data display.

By setting READ UNCOMMITTED, the website was able to read data without waiting for the write transaction to complete. This helped avoid the read operation getting blocked by the Windows service transaction.

However, this approach should be used carefully. READ UNCOMMITTED can return dirty reads, which means the website may read changes that are not committed yet.

If the write transaction is rolled back later, the displayed data may not match the final database state.

So this approach is suitable only when the screen can tolerate temporary data inconsistency.

We have many ways to resolve deadlock issues. Here I am only discussing how to prevent deadlock in Entity Framework.

There are options like this [click here] (https://learn.microsoft.com/en-us/sql/t-sql/statements/set-transaction-isolation-level-transact-sql),  and use of a store procedure with a NOLOCK keyword (Select * from Test NOLOCK) in a query.

This stored procedure is called from the entity framework. Also, we can use SQL View with an NOLOCK keyword in a query to prevent deadlock.

To overcome this issue we have to implement a single solution for the whole project, which is READ UNCOMMITTED data to display on a website.

Entity framework uses SQL server transaction ISOLATION LEVEL  by default which READ COMMITTED data. We have updated the ASP.NET MVC C# code to always read uncommitted data by setting the isolation level.

Kindly follow the ASP.NET C# code, though you can resolve the deadlock issue in the asp.net MVC project. The following code shows all READ UNCOMMITTED data on the website.

Code Explanation

The following EF6 example shows how to open the database connection and set the transaction isolation level to READ UNCOMMITTED before running read operations.
This can be useful for read-only pages where temporary inconsistency is acceptable. For critical workflows, developers should consider more secure options before applying this globally.

Example Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using Repositories;
using Repositories.EntityFramework;
using System.Data;

namespace Web.Controllers
{
    public class TestController : Controller
    {
        // dbContext
        private DBContext dbContextReadOnly = new DBContext();
        
        // Repository
        private IStudentRepository studentRepository { get; set; }

        // Close Connection
        protected override void Dispose(bool disposing)
        {
            try
            {
                base.Dispose(disposing);
            }
            finally
            {
                if (dbContextReadOnly.Database.Connection.State == ConnectionState.Open)
                {
                    dbContextReadOnly.Database.Connection.Dispose();
                }
            }
        }
        public TestController()
        {
            InitialiseController();
        }

        public void InitialiseController()
        {
            // Check DB connection
            if (dbContextReadOnly.Database.Connection.State == ConnectionState.Closed)
            {
                // SET TRANSACTION ISOLATION LEVEL
                dbContextReadOnly.Database.Connection.Open();
                dbContextReadOnly.Database.ExecuteSqlCommand("SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;");
            }

            // Initialise Repository
            studentRepository = new StudentRepository(dbContextReadOnly);
        }

        public ActionResult Index()
        {
            // Read lock data
            try
            {
                // Read locked table data
                var studentList = studentRepository.Query.ToList();

                // Read locked item
                var student = studentRepository.Query.Where(x => x.Id == 1).FirstOrDefault();
                
                return View(student);
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }
        [HttpPost]
        public ActionResult Index(int id)
        {
            // Add/Update/Delete data using TransactionScope
            using (var dbContextWriteOnly = new DBContext())
            {
                using (var transactionResult = dbContextWriteOnly.Database.BeginTransaction(IsolationLevel.ReadUncommitted))
                {
                    // Re-Initialise Repository
                    studentRepository = new StudentRepository(dbContextWriteOnly);

                    try
                    {
                        var student = studentRepository.Query.Where(x => x.Id == id).FirstOrDefault();
                        student.DateTimeStamp = DateTime.Now;
                        studentRepository.SaveChanges();
                        transactionResult.Commit();

                        return View();
                    }
                    catch (Exception ex)
                    {
                        transactionResult.Rollback();
                        throw ex;
                    }
                }
            }
        }
    }
}

When Should You Use READ UNCOMMITTED?

READ UNCOMMITTED can be considered when the application only needs to display non-critical data and temporary inconsistency is acceptable.
It may be suitable for:

• Activity logs
• Dashboard widgets
• Internal reports
• Search result pages
• Read-only listing screens
• Non-financial summary data

Avoid using READ UNCOMMITTED for:

• Payment data
• Accounting records
• Inventory quantity
• Order status
• Customer balances
• Approval workflows
• Audit-sensitive data

This matters because READ UNCOMMITTED can read data that is later rolled back. Microsoft also explains that dirty reads happen when a transaction reads data that has not yet been committed.

Pros and Cons of Using Read-Uncommitted and SQL NoLock

• https://sqlblog.com/blogs/tamarick_hill/archive/2013/05/06/pros-cons-of-using-read-uncommitted-and-nolock.aspx

Reference Links

• https://msdn.microsoft.com/en-us/data/dn456843.aspx
• https://msdn.microsoft.com/en-IN/library/ms173763.aspx
• https://blogs.msdn.microsoft.com/diego/2012/03/31/tips-to-avoid-deadlocks-in-entity-framework-applications/

Safer Solutions to Reduce SQL Server Deadlocks

READ UNCOMMITTED is not the only way to reduce deadlocks. In many applications, it is better to fix the root cause instead of allowing dirty reads.
Safer options include:
Keep Transactions Short

Long-running transactions hold locks for longer. Keep only required database operations inside the transaction.
Add Proper Indexes

Missing indexes can force SQL Server to scan more rows, which increases locking and blocking.
Read-Only Required Columns

Avoid loading full entities when only a few fields are needed.
Use AsNoTracking for Read-Only Queries

For read-only Entity Framework queries, AsNoTracking can reduce tracking overhead because EF does not need to track changes for returned entities.
Access Tables in the Same Order

When multiple processes update related tables, keep the table access order consistent to reduce circular waits.
Add Retry Logic

SQL Server may choose one transaction as the deadlock victim. The application should catch deadlock errors and retry the operation where safe.
Consider Snapshot-Based Isolation

For some systems, snapshot-based isolation can reduce reader/writer blocking without allowing dirty reads. Microsoft’s SQL Server guide discusses row versioning and snapshot isolation as alternatives to locking-based behavior.

READ UNCOMMITTED vs READ COMMITTED vs Snapshot Isolation

READ UNCOMMITTED

Allows reading uncommitted data. Helps reduce blocking but can return dirty or inconsistent data.
READ COMMITTED

SQL Server default isolation level. It prevents dirty reads, but readers and writers may block each other depending on database settings.
Snapshot-Based Isolation

Uses row versioning so readers can work with committed versions of data instead of waiting for active write locks. This can reduce blocking, but it needs proper testing before enabling it in production.
Microsoft documentation says READ COMMITTED is the SQL Server default and prevents dirty reads. It also explains that READ UNCOMMITTED is the least restrictive isolation level and can read uncommitted changes.

How to Diagnose Entity Framework SQL Server Deadlocks

Before changing isolation levels, developers should first confirm where the deadlock is happening.
Useful checks include:

• Review the SQL Server deadlock graph.
• Check which queries are involved.
• Identify tables and indexes used by both processes.
• Check transaction duration.
• Review background jobs and scheduled tasks.
• Look for unnecessary include statements or large result sets.
• Check whether queries are loading full entities instead of selected fields.
• Review whether multiple processes access tables in a different order.

This helps avoid applying READ UNCOMMITTED where the real issue is query design, indexing, or transaction scope.

Best Practices to Prevent Deadlocks in EF6 and SQL Server

To reduce deadlock chances in EF6 applications:

• Keep transactions short.
• Do not include long business logic inside database transactions.
• Use proper indexes on frequently filtered columns.
• Load only required data.
• Use read-only query templates for display screens.
• Keep table access order consistent.
• Avoid unnecessary locks.
• Add retry logic for deadlock victim errors.
• Monitor deadlock graphs in SQL Server.
• Avoid applying READ UNCOMMITTED globally without checking data correctness risks.

Conclusion

Entity Framework and SQL Server deadlocks usually happen when read and write operations compete for the same locked data. In this project, the issue appeared because a Windows service was updating data while the website was trying to read from the same tables.
Using READ UNCOMMITTED helped the website read data without waiting for the write transaction to complete. But this approach should not be treated as a universal fix because it can return dirty or temporary data.
For non-critical read-only screens, READ UNCOMMITTED can be useful. For sensitive business workflows, developers should first review transaction length, indexing, query design, retry logic, and snapshot-based isolation options.
If your ASP.NET MVC or Entity Framework application is facing SQL Server deadlocks, Satva Solutions can help review the database flow, identify blocking points, and implement a safer fix based on your application needs.

The recommended technique for resolving Deadlock issues in entity framework 6 is the easiest way and time-saving for ASP.NET MVC Developers.

With the use of isolation level, We can show READ UNCOMMITTED information on the ASP.NET MVC website like the above example. we have lots of tips and tricks related to asp.net MVC development.

For more information,  Go to the ISOLATION LEVEL option.

Thank you for reading.

FAQs

What causes deadlocks in Entity Framework and SQL Server?

Deadlocks happen when two or more database operations wait for each other to release locks. In Entity Framework applications, this often happens when background jobs and web requests read or update the same data at the same time.

What does “chosen as the deadlock victim” mean?

It means SQL Server detected a deadlock and stopped one transaction so the other transaction could continue. The stopped transaction must be retried if the operation is still required.

Does READ UNCOMMITTED fix SQL Server deadlocks?

READ UNCOMMITTED can reduce blocking for read operations, but it does not fix every deadlock. It should be used only when dirty or temporary data is acceptable.

Is READ UNCOMMITTED the same as NOLOCK?

In SQL Server, READ UNCOMMITTED has the same effect as applying NOLOCK to all SELECT statements in that transaction. Microsoft confirms this in its isolation level documentation.

Is READ UNCOMMITTED safe for production?

It depends on the use case. It may be acceptable for non-critical read-only screens, but it should not be used for financial, inventory, payment, approval, or audit-sensitive data.

How can I prevent EF6 deadlocks without dirty reads?

You can reduce deadlocks by keeping transactions short, adding indexes, reducing large reads, accessing tables in the same order, using retry logic, and considering snapshot-based isolation after proper testing.