Ef_Tricks.cs

// Defining a Shadow Property
public class ApplicationDbContext : DbContext
{
    public DbSet<Book> Books { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Book>().Property<DateTime>("ModifiedDate");
    }
}

public class Book
{
    public int Id { get; set; }
    public string Title { get; set; }
}

// Using Shadow Properties in a Query
using (var context = new ApplicationDbContext())
{
    var books = context.Books
        .OrderByDescending(b => EF.Property<DateTime>(b, "ModifiedDate"))
        .ToList();
}
//=======================================================
// Implementing TPH Inheritance
public abstract class Employee
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class FullTimeEmployee : Employee
{
    public decimal Salary { get; set; }
}

public class PartTimeEmployee : Employee
{
    public decimal HourlyRate { get; set; }
}

// Configure DbContext
public class ApplicationDbContext : DbContext
{
    public DbSet<Employee> Employees { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<FullTimeEmployee>();
        modelBuilder.Entity<PartTimeEmployee>();
    }
}

// Querying TPH Inheritance
using (var context = new ApplicationDbContext())
{
    // Returns a list of Employee objects (FullTimeEmployee and PartTimeEmployee instances)
    var employees = context.Employees.ToList(); 
}

using (var context = new ApplicationDbContext())
{
    var fullTimeEmployees = context.Employees.OfType<FullTimeEmployee>().ToList();
    var partTimeEmployees = context.Employees.OfType<PartTimeEmployee>().ToList();
}
//=======================================================
// Eager Loading with Projections
public class Blog
{
    public int Id { get; set; }
    public string Title { get; set; }
    public ICollection<Post> Posts { get; set; }
}

public class Post
{
    public int Id { get; set; }
    public string Title { get; set; }
    public int BlogId { get; set; }
    public Blog Blog { get; set; }
}


public class BlogWithPostTitles
{
    public string BlogTitle { get; set; }
    public List<string> PostTitles { get; set; }
}


using (var context = new ApplicationDbContext())
{
    var blogsWithPostTitles = context.Blogs
        .Select(b => new BlogWithPostTitles
        {
            BlogTitle = b.Title,
            PostTitles = b.Posts.Select(p => p.Title).ToList()
        })
        .ToList();
}

//=======================================================
// Batch Operations
// Install-Package EFCore.BulkExtensions

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

Instead of inserting each Product individually, you can use the BulkInsert method to perform a batch operation:

using (var context = new ApplicationDbContext())
{
    // Assume this method returns a list of products
    List<Product> products = GetProducts(); 

    context.BulkInsert(products);
}

//=======================================================
// Lazy Loading
// Install-Package Microsoft.EntityFrameworkCore.Proxies

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
    optionsBuilder
        .UseLazyLoadingProxies()
        .UseSqlServer("your_connection_string");
}


public class Author
{
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual ICollection<Book> Books { get; set; }
}

public class Book
{
    public int Id { get; set; }
    public string Title { get; set; }
    public virtual Author Author { get; set; }
}
//=======================================================
// Powerful Custom Conventions
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    foreach (var entityType in modelBuilder.Model.GetEntityTypes())
    {
        // Set table names to uppercase
        entityType.SetTableName(entityType.GetTableName().ToUpper());

        // Set column names to lowercase
        foreach (var property in entityType.GetProperties())
        {
            property.SetColumnName(property.GetColumnName().ToLower());
        }
    }
}

//=======================================================
// Event Listeners for Tracing and Logging

public class SqlQueryLoggingListener : IDiagnosticsLogger<DbLoggerCategory.Query>
{
    public bool IsEnabled(LogLevel logLevel) => logLevel == LogLevel.Information;

    public void Log<TState>(LogLevel logLevel, DbLoggerCategory.Query eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
    {
        if (IsEnabled(logLevel))
        {
            Console.WriteLine(formatter(state, exception));
        }
    }
}

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
    optionsBuilder
        .UseSqlServer(connectionString)
        .AddInterceptors(new SqlQueryLoggingListener());
}

//=======================================================
// Optimizing Data Seeding
protected override void Up(MigrationBuilder migrationBuilder)
{
    migrationBuilder.InsertData(
        table: "MyTable",
        columns: new[] { "Id", "Name" },
        values: new object[] { 1, "My First Seed Data" });
}


//Using Bulk Inserts for Large Data Sets
using EFCore.BulkExtensions;
using MyProject.Data;

using (var context = new MyDbContext())
{
    var data = new List<MyEntity>
    {
        new MyEntity { Id = 1, Name = "Data 1" },
        // ...
        new MyEntity { Id = 1000, Name = "Data 1000" }
    };

    context.BulkInsert(data);
}
//Applying Conditional Seeding
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
#if DEBUG
    modelBuilder.Entity<MyEntity>().HasData(
        new MyEntity { Id = 1, Name = "Seed Data for Debug" });
#endif
}

//=======================================================
//Efficiently Mapping Complex Types

//Using Owned Entity Types
public class Customer
{
    public int Id { get; set; }
    public string Name { get; set; }
    public Address Address { get; set; }
}

public class Address
{
    public string Street { get; set; }
    public string City { get; set; }
    public string ZipCode { get; set; }
}

public class MyDbContext : DbContext
{
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Customer>().OwnsOne(c => c.Address);
    }
}

//Using Value Converters
public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public List<string> Tags { get; set; }
}

public class MyDbContext : DbContext
{
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Product>()
            .Property(p => p.Tags)
            .HasConversion(
                v => JsonConvert.SerializeObject(v),
                v => JsonConvert.DeserializeObject<List<string>>(v));
    }
}

//Using Custom Mappings
public class Order
{
    public int Id { get; set; }
    public string CustomerName { get; set; }
    public decimal Total { get; set; }
    public Money Currency { get; set; }
}

public class Money
{
    public decimal Amount { get; set; }
    public string CurrencyCode { get; set; }
}

public class MyDbContext : DbContext
{
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Order>()
            .Property(o => o.Currency.Amount)
            .HasColumnName("TotalAmount");

        modelBuilder.Entity<Order>()
            .Property(o => o.Currency.CurrencyCode)
            .HasColumnName("CurrencyCode");
    }
}

//=======================================================
//Custom Entity Materialization

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

    // Custom constructor for materialization
    public Product(int id, string name, decimal price)
    {
        Id = id;
        Name = name;
        Price = ApplyDiscount(price);
    }

    private decimal ApplyDiscount(decimal price)
    {
        // Apply a custom discount based on the price
        return price * 0.9m;
    }
}

using (var context = new MyDbContext())
{
    var products = context.Products
        .FromSqlRaw("SELECT Id, Name, Price FROM Products")
        .ToList();
}