Interview Question

How can you update an existing entity in Entity Framework Core?

Answer

There are several ways to update entities in EF Core. Here are the main approaches:

1. Track and Update

using (var context = new ApplicationDbContext())
{
    var customer = await context.Customers.FindAsync(1);
    customer.Name = "Updated Name";
    await context.SaveChangesAsync();
}

2. Update Without Querying

using (var context = new ApplicationDbContext())
{
    var customer = new Customer 
    { 
        Id = 1, 
        Name = "Updated Name" 
    };
    context.Customers.Update(customer);
    await context.SaveChangesAsync();
}

3. Updating Specific Properties

using (var context = new ApplicationDbContext())
{
    var customer = new Customer { Id = 1 };
    context.Customers.Attach(customer);
    context.Entry(customer).Property(x => x.Name).IsModified = true;
    customer.Name = "Updated Name";
    await context.SaveChangesAsync();
}

Key Points 💡

• First approach is best when you need to validate existing data
• Second approach is efficient when you know the entity exists
• Third approach is best for partial updates
• Always consider concurrency handling

Common Follow-up Questions

1. How do you handle concurrency conflicts?
2. What’s the difference between Update and Attach?
3. How can you update multiple entities efficiently?