Understanding DbContext

DbContext is the primary class that coordinates Entity Framework functionality for a given data model. It represents a session with the database and can be used to query and save instances of your entities.

Key Responsibilities

1. Database Connection Management
   • Manages database connections
   • Handles connection string configuration
   • Provides transaction support
2. Query Management
   • Converts LINQ to SQL
   • Tracks query results
   • Manages caching
3. Change Tracking
   • Tracks entity modifications
   • Records insert/update/delete operations
   • Manages entity states
4. Data Persistence
   • Saves tracked changes to database
   • Handles concurrency
   • Manages transactions

Creating a DbContext

public class ApplicationDbContext : DbContext
{
    // DbSet properties for your entities
    public DbSet<Customer> Customers { get; set; }
    public DbSet<Order> Orders { get; set; }

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

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        // Configure entity relationships, constraints, etc.
        modelBuilder.Entity<Order>()
            .HasOne(o => o.Customer)
            .WithMany(c => c.Orders);
    }
}

Using DbContext

using (var context = new ApplicationDbContext())
{
    // Querying data
    var customers = context.Customers
        .Where(c => c.Country == "USA")
        .ToList();

    // Adding new data
    var newCustomer = new Customer { Name = "John Doe" };
    context.Customers.Add(newCustomer);

    // Updating data
    var customer = context.Customers.First();
    customer.Name = "Jane Doe";

    // Deleting data
    context.Customers.Remove(customer);

    // Save all changes
    context.SaveChanges();
}

Best Practices

1. Lifetime Management
   • Use dependency injection
   • Create scoped instances
   • Dispose properly
2. Configuration
   • Use separate configuration classes
   • Apply conventions consistently
   • Document relationships
3. Performance
   • Use async methods
   • Enable change tracking only when needed
   • Use projections for read-only queries
4. Error Handling
   • Handle concurrency conflicts
   • Implement retry logic
   • Log database errors