[转]How to Improve Entity Framework Add Performance?

本文转自：http://entityframework.net/improve-ef-add-performance

When you overuse the Add() method for multiple entities, your application suffers from performance issues.

using (var ctx = new CustomerContext())

{

    foreach(var line in lines)

    {

        var customer = new Customer();

        // ...code...

        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

Is Entity Framework Add Really Slow?

In fact, the Add method is not slow at all. Adding an entity to a list cannot be that slow. It‘s the DetectChanges method invoked inside the Add method which is insanely slow!

Using the Add method in a loop is usually a poor practice which impacts your application performance severely when poorly used.

• USE AddRange over Add (Recommended)
• SET AutoDetectChanges to false
• SPLIT SaveChanges in multiple batches

Use AddRange over Add (Recommended)

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

Why?

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

}

Try it online

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!

}

Try it online

SPLIT SaveChanges into multiple batches

This solution is not recommended. When adding multiple entities, split entities with a batch size in multiple different contexts.

Why?

More tracking entities your context contains, slower the DetectChanges method is! So by reducing the number of entities by context, you improve the performance.

Performance Comparisons

Note:

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

How

1. CREATE a 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!

Try it online

[转]How to Improve Entity Framework Add Performance?

原文：https://www.cnblogs.com/freeliver54/p/9507049.html