Create Database Views using EF Core Code First approach

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06-10-2024

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Simplifying Data Access with EF Core Code First Views

Data views are a powerful tool in database management, offering a simplified and focused way to access data. Using Entity Framework Core (EF Core) with the Code First approach, you can easily define and manage database views within your application code. This article will guide you through the process, explaining the benefits and showcasing practical examples.

The Problem:

Imagine you have a complex database schema with multiple tables and relationships. You want to create a simplified view that combines data from different tables to meet specific reporting or analysis needs. Manually creating SQL views can be cumbersome and prone to errors, especially when dealing with complex relationships.

The Solution: EF Core Code First Views

EF Core's Code First approach offers a convenient way to define database views directly within your application's code. You can leverage the power of C# syntax and LINQ to express your view logic, keeping it consistent with your domain model.

Scenario:

Let's consider a scenario where you have two tables: Customers and Orders. You want to create a view called CustomerOrdersView that displays customer information along with the total order amount for each customer.

Original Code:

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;

public class Customer
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }

    public ICollection<Order> Orders { get; set; }
}

public class Order
{
    public int Id { get; set; }
    public int CustomerId { get; set; }
    public decimal Amount { get; set; }

    public Customer Customer { get; set; }
}

public class CustomerOrdersView
{
    public int CustomerId { get; set; }
    public string CustomerName { get; set; }
    public decimal TotalOrderAmount { get; set; }
}

public class ApplicationDbContext : DbContext
{
    public DbSet<Customer> Customers { get; set; }
    public DbSet<Order> Orders { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        // Define the CustomerOrdersView
        modelBuilder.Entity<CustomerOrdersView>(entity =>
        {
            entity.HasNoKey();
            entity.ToView("CustomerOrdersView");

            entity.Property(e => e.CustomerId)
                .HasColumnName("CustomerId");

            entity.Property(e => e.CustomerName)
                .HasColumnName("CustomerName");

            entity.Property(e => e.TotalOrderAmount)
                .HasColumnName("TotalOrderAmount");
        });
    }
}

Analysis & Explanation:

• Defining the View Model: The CustomerOrdersView class represents the structure of the view, defining properties for CustomerId, CustomerName, and TotalOrderAmount.
• Entity Configuration: Within the OnModelCreating method, we configure the CustomerOrdersView entity:
  • HasNoKey(): Specifies that the view doesn't have a primary key.
  • ToView("CustomerOrdersView"): Sets the name of the view in the database.
  • Property(e => e.CustomerId).HasColumnName("CustomerId"): Maps the property to a corresponding column in the view. This is important for ensuring correct data mapping.
• View Logic (not shown): The OnModelCreating method is where you would typically implement the view logic using LINQ queries. This example focuses on the basic structure, and the actual view query would be defined here.

Benefits of Using EF Core Code First Views:

• Code-First Convenience: Define and manage views directly in your application code, keeping them close to your domain model.
• LINQ-Based Logic: Leverage the power of LINQ to express complex view queries with ease and readability.
• Simplified Data Access: Views provide a simplified interface to access data, hiding the underlying complexity of table relationships.
• Maintainability: Centralized view definitions within your application code make them easier to maintain and update.

Additional Value:

• Complex View Scenarios: EF Core Code First can handle complex view scenarios involving joins, aggregations, and other advanced SQL operations, all expressed in a concise and readable C# syntax.
• Customization: You can customize the view's structure and behavior by adding constraints, computed columns, or filtering conditions.

References & Resources:

• Entity Framework Core Documentation
• Code First Conventions

By leveraging EF Core Code First Views, you can effectively manage and simplify your database access logic, enabling cleaner and more maintainable application code.