LINQ vs IQueryable?

LINQ vs IQueryable

What interviewers test

• Deferred execution
• DB performance

LINQ (IEnumerable)

var data = users.Where(x => x.Age > 30).ToList();

• Executes in memory

IQueryable

var data = db.Users.Where(x => x.Age > 30);

• Translates to SQL
• Executes in DB

Interview line

“IQueryable builds expressions; IEnumerable executes them.”

🔟 Write clean, production-ready C# code

What interviewers test

• Professional maturity

Principles

• Small methods
• Clear naming
• No magic values
• Proper exceptions

public class OrderService
{
public void PlaceOrder(Order order)
{
if (order == null)

throw new ArgumentNullException(nameof(order));

Validate(order);

Save(order);

}
private void Validate(Order order)
{
if (order.Total <= 0)

throw new InvalidOperationException("Invalid total");

}
private void Save(Order order)
{

// persistence logic

}
}