This document provides guidelines for optimizing Entity Framework performance. Some key recommendations include: avoiding retrieving unnecessary data; using compiled queries; filtering data before calling ToList(); and leveraging eager loading instead of lazy loading to reduce database hits. It also suggests using raw SQL or stored procedures when Entity Framework queries cannot be optimized.

1. Entity
Framework
Optimization
By Rajeev Harbola

2. Design Consideration
 Avoid to put all the DB Objects into One Single Entity Model.
 Disable change tracking for entity if not needed.
NorthwindDataContext context = new NorthwindDataContext()
context.tblCities.MergeOption = MergeOption.NoTracking;
 Avoid fetching all the fields if not required
//Bad Practice
var customer = (from cust in dataContext.Customers select cust).ToList();
//Good Practice
var customer = (from cust in dataContext.Customers
select new {
customer. CustomerID,customer.Name,customer.Address}ToList ();
 Use Compiled Query wherever needed

3. Design Consideration
• Avoid using Contains
• Retrieve only required number of records.

4. Coding Guidelines
• Do Not Count After Query Execution
var empCount = db.Employees .Where(x => x.CreateDate <
DateTime.Now.AddDays(-10) .Count() //only executes a SQL COUNT
var emps = db.Employees .Where(x => x.CreateDate <
DateTime.Now.AddDays(-10)
var empCount = emps.Count() // returns all matching employees and
then executes a count
• Filter Before ToList()
//ToList() executed too early
var emps = db.Employees .Where(x => x.CreateDate <
DateTime.Now.AddDays(-10) .ToList() // All employees created within last 10 days queried
.Take(50) // List is filtered for the top 50
//ToList() executed last
var emps = db.Employees .Where(x => x.CreateDate <
DateTime.Now.AddDays(-10) .Take(50) .ToList() //Query made for top
50 employees created within last 10 days

5. Coding Guidelines
• Don’t Load Entities To Delete Them (very important)
var emp = db.Employees.Find(empID); //Executes a query against the database
db.Employees.Remove(emp);
db.SaveChanges(); //Executes a second hit to the database
var emp = new Employee { ID = empID }
db.Employees.Attach(emp);
db.Employees.Remove(emp);
db.SaveChanges(); //Executes a single hit to the database
• Use Eager Loading Instead of Lazy Loading
var employees = db.Employees; foreach(var emp in employees)
{
var address = emp.Address; //Database query is executed every time this line is hit
}
var employees = db.Employees .Include(x => x.Address) .ToList(); //All data loaded from
database
foreach(var emp in employees)
{
var address = emp.Address; //No database query executed
}

6. Coding Guidelines
• Query In-Memory Entities First
var emp = db.Employees.Find(empID); //Executes a query against the database
db.Employees.Remove(emp);
db.SaveChanges(); //Executes a second hit to the database
var emp = new Employee { ID = empID }
db.Employees.Attach(emp);
db.Employees.Remove(emp);
db.SaveChanges(); //Executes a single hit to the database
• Use Eager Loading Instead of Lazy Loading
var emp = db.Employees.Find(empID); // Queries in memory first
var emp = db.Employees.Where(x => x.ID == empID); //Always hits the database
var emp = db.Employees.Local.Where(x => x.ID == empID) ;

7. Advanced
• Use Compiled Query wherever needed
// create the entity object
NorthwindEntities mobjentity = new NorthwindEntities();
//Simple Query
IQueryable lstCus = from customer in mobjentity.tblCustomers where customer.City == "Delhi"
select customer;
//Compiled Query
Func> compiledQuery= CompiledQuery.Compile>((ctx, city) =>from customer in ctx.Customers
where customer.City == city
select customer);
• Debug and Optimize LINQ Query
IQueryable lstCus = from customer in mobjentity.tblCustomers
where customer.City == "Delhi"
select customer;
lstCus.Dump();

8. Last but not least
• Don’t Rely on Entity Framework Exclusively For Data
Access
• Finally, EF is great for productivity but executing raw SQL
or a stored procedure may often produce performance
benefits.
• In EF 4.0 and above the DbContext the SQLQuery()
method to execute raw SQL:
• var emps = db.Database.SQLQuery("select email from
Employees");Similarly use ExecuteSqlCommand() to
execute a stored procedure:
• var emps = db.Database.ExecuteSqlCommand("...");

9. THANKS
&
No question please