Why should you care?

ShopNest product cards need Id, Name, Price, ThumbnailUrl — not full description blobs or internal cost fields.

See it live — copy this example

Paste into a .NET project with EF Core packages, then run with LocalDB/SQL Server (dotnet ef / dotnet run).

var cards = await _context.Products
    .Where(p => p.IsPublished)
    .Select(p => new ProductCardDto
    {
        Id = p.Id,
        Name = p.Name,
        Price = p.Price,
        CategoryName = p.Category!.Name
    })
    .ToListAsync();

What happened?

• Select with DTO maps to SQL SELECT listing only projected columns plus JOIN to Category for Name — no full Product entity materialized.

Practice next

1. Replace ToList of entities with Select to DTO.
2. Compare network payload size before and after.
3. Project nested collections carefully — can cause cartesian explosion.
4. Add computed DiscountPrice = p.Price * 0.9m inside Select.
5. Project to record type instead of class for immutable API models.

Remember

Select projects columns and shapes in SQL. DTO projection reduces data transfer. Avoid loading entities when DTO suffices.

ShopNest mobile listing

Mobile API projects ProductCardDto with category name in one JOIN query.

Outcome: 70% smaller JSON responses on 4G networks during browse.