Entity Framework DetectChanges Discover How to Improve Performance

How to Improve Entity Framework DetectChanges Performance?

When you track multiple entities in your context, then your application will suffer from performance issues causing by Entity Framework DetectChanges method.

using (var ctx = new CustomerContext())
{
    foreach(var line in lines)
    {
        var customer = new Customer();
        // ...code...
        
        // DetectChanges is invoked every time you call Add
        ctx.Customers.Add(customer);
    }
    
    ctx.SaveChanges();
}

StackOverflow Related Questions

• WebAPI EF update 30,000 rows of data is very slow
• Performance of Entity Framework [closed]

Answer

• REDUCE the amount of entities in your context
• REDUCE the number of DetectChanges
• SET AutoDetectChanges to false

REDUCE the number of entities in your context

When adding/modifying multiple entities, split your logic into numerous batches to have fewer records in the context.

Why?

More tracking entities your context contains, slower the DetectChanges method is!

Performance Comparisons

Note:

• *: SaveChanges time not included
• **: Entity with two relations

How?

1. CREATE batchSize variable
2. CALL SaveChanges before creating a new batch
3. CALL SaveChanges
4. Done!

// 1. CREATE a batchSize variable
int batchSize = 400;
		
var context = new EntityContext();

for(int i = 0; i <= 2000; i++)
{
    // 2. CALL SaveChanges before creating a new batch
    if (i != 0 && i%batchSize == 0)
    {
    	context.SaveChanges();
    	context = new EntityContext();
    }
    
    var customer = new Customer();
    // ...code...
    
    context.Customers.Add(customer);
}

// 3. CALL SaveChanges
context.SaveChanges();

// 4. Done!

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Reduce the number of DetectChanges

When adding multiple entities, you should always use Entity Framework AddRange once with a list instead of calling various time the Add method.

Why?

• The Add method DetectChanges after every records added.
• The AddRange method DetectChanges after all records is added.

Performance Comparisons

Note:

• *: SaveChanges time not included
• **: Entity with two relations

How?

1. CREATE a list
2. ADD entity to the list
3. USE AddRange with the list
4. SaveChanges
5. Done!

using (var context = new EntityContext())
{
    // 1. CREATE a list
    List<Customer>  list = new List<Customer>();
    
    for(int i = 0; i < 2000; i++)
    {
        var customer = new Customer();
        // ...code...
    
        // 2. ADD entity to the list
    	list.Add(customer);
    }
	
    // 3. USE AddRange with the list		
    context.Customers.AddRange(list);
	
    // 4. SaveChanges
    ctx.SaveChanges();
    
    // 5. Done!
}

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SET AutoDetectChanges to false

When adding multiple entities, if you cannot use AddRange, set Entity Framework AutoDetectChanges to false

Why?

• The Add method DetectChanges after every records added.

By disabling AutoDetectChanges, the DetectChanges method will only be invoked when you do it.

Performance Comparisons

Note:

• *: SaveChanges time not included
• **: Entity with two relations

How?

1. SET AutoDetectChangesEnabled = false
2. CALL DetectChanges before SaveChanges
3. SaveChanges
4. Done!

using (var context = new EntityContext())
{
    // 1. SET AutoDetectChangesEnabled = false
    context.Configuration.AutoDetectChangesEnabled = false;
     
    List<Customer>  list = new List<Customer>();

    for(int i = 0; i < 2000; i++)
    {
        var customer = new Customer();
        // ...code...
    
    	list.Add(customer);
    }
    
    context.Customers.AddRange(list);
    
    // 2. CALL DetectChanges before SaveChanges
    context.ChangeTracker.DetectChanges();
    
    // 3. SaveChanges
    context.SaveChanges();
    
    // 4. Done!
}

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