EF Core - Models

In Entity Framework Core (EF Core), models represent the structure of your data as classes that map to database tables. Defining models is a fundamental part of using EF Core, as it allows you to work with your data using objects instead of database tables and SQL. This tutorial explores how to define and configure models in EF Core.

1. Defining Models

Models in EF Core are defined as classes with properties that map to columns in a database table. Each model class represents an entity in your application.

        
            
public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}
        
    

In this example, the Product class represents a database table with columns for Id, Name, and Price.

2. Configuring Models

EF Core allows you to configure models using data annotations or the Fluent API to define how your classes map to database tables and columns.

Data Annotations Example:

        
            
public class Product
{
    [Key]
    public int Id { get; set; }

    [Required]
    [MaxLength(100)]
    public string Name { get; set; }

    [Range(0, 9999.99)]
    public decimal Price { get; set; }
}
        
    

Fluent API Example:

        
            
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Product>()
        .Property(p => p.Name)
        .IsRequired()
        .HasMaxLength(100);

    modelBuilder.Entity<Product>()
        .Property(p => p.Price)
        .HasColumnType("decimal(18,2)");
}
        
    

3. Relationships

EF Core supports various types of relationships between entities, including one-to-one, one-to-many, and many-to-many. You can define these relationships using navigation properties and configuration.

        
            
public class Order
{
    public int Id { get; set; }
    public DateTime OrderDate { get; set; }
    public ICollection<OrderItem> OrderItems { get; set; }
}

public class OrderItem
{
    public int Id { get; set; }
    public int OrderId { get; set; }
    public Order Order { get; set; }
    public string ProductName { get; set; }
    public decimal Price { get; set; }
}
        
    

In this example, the Order entity has a one-to-many relationship with the OrderItem entity, indicated by the OrderItems navigation property.

4. Best Practices for Model Design

Designing your models effectively is crucial for building scalable and maintainable applications. Here are some best practices to consider:

• Use Explicit Key Properties: Always define a primary key for your entities using the Id or [Key] attribute.
• Normalize Data: Use normalization principles to design your tables, ensuring that each table stores information about a single entity type.
• Use Navigation Properties: Leverage navigation properties to define relationships and navigate between related entities.
• Configure Model with Fluent API: Prefer the Fluent API for complex configurations and to maintain separation between model classes and configuration.
• Use Value Conversions: When necessary, use EF Core's value conversions to store custom data types in your database.
• Apply Validation: Use data annotations and validation attributes to ensure data integrity and apply business rules.

Summary

Models in EF Core are a critical aspect of your application's data layer, providing a way to represent and manipulate data as objects. By following best practices and using the configuration options available, you can design models that are efficient, scalable, and maintainable.