Loading Strategies - (EF Querying with LINQ)

Entity Framework (EF) is a popular ORM (Object-Relational Mapping) tool for .NET applications. When working with EF, it's important to use the appropriate loading strategy, depending on your specific requirements. In this tutorial, we'll go over some common loading strategies and how to use them in EF with LINQ.

Syntax

There is no specific syntax for loading strategies in EF with LINQ.

Example

Assume we have two entities in our EF model, Order and Product, with a many-to-many relationship between them. Here's an example of loading the products for a specific order using different loading strategies:

// Eager loading -- loads both the order and its products in a single query
var order = dbContext.Orders.Include(o => o.Products).FirstOrDefault(o => o.Id == orderId);

// Explicit loading -- loads the order first, then the products for that order in a separate query
var order = dbContext.Orders.FirstOrDefault(o => o.Id == orderId);
dbContext.Entry(order).Collection(o => o.Products).Load();

// Lazy loading -- loads the order first, then loads the products for that order when accessed
var order = dbContext.Orders.FirstOrDefault(o => o.Id == orderId);

// Access the products for the order to trigger lazy loading
var products = order.Products.ToList();

Explanation

There are three common loading strategies that can be used with EF and LINQ:

• Eager loading: loads related entities in a single query using the Include method.
• Explicit loading: loads related entities in a separate query after the primary entity has been loaded.
• Lazy loading: loads related entities only when they're accessed by the code.

Eager and explicit loading are more efficient when loading entities with relationships, while lazy loading can lead to performance problems if overused.

Use

Choose the appropriate loading strategy based on your application's specific requirements. If the relationships are frequently used throughout the application, using eager or explicit loading is more efficient. If the relationships are only used occasionally, or if you're unsure about the usage, lazy loading can be utilized.

Important Points

Here are some important points to keep in mind when working with loading strategies in EF with LINQ:

• Choose the appropriate loading strategy for your application's specific requirements.
• Eager and explicit loading are more efficient when working with entities with relationships.
• Lazy loading can lead to performance issues if overused.

Summary

In this tutorial, we went over different loading strategies when working with EF and LINQ. We covered the syntax, examples, explanation, use, and important points of using eager, explicit, and lazy loading strategies. By understanding these concepts, you can choose the appropriate loading strategy for your application and improve performance.