Projection (EF Core)

ℹ️ Description: Use ProjectTo() with Entity Framework to translate mappings to SQL for better performance.

Code Example


                // Instead of this (inefficient):
                var users = dbContext.Users.ToList();
                var userDTOs = _mapper.Map>(users);

                // Do this (efficient):
                var userDTOs = dbContext.Users
                    .ProjectTo(_mapper.ConfigurationProvider)
                    .ToList();

⚡ Why ProjectTo is Important

Without ProjectTo (Inefficient)

// Retrieves ALL columns from User table
var users = await dbContext.Users.ToListAsync();

// Maps in memory (after loading all data)
var userDTOs = _mapper.Map<List<UserDTO>>(users);

With ProjectTo (Efficient)

// ProjectTo translates mapping to SQL
// Only retrieves columns needed for UserDTO
var userDTOs = await dbContext.Users
    .ProjectTo<UserDTO>(_mapper.ConfigurationProvider)
    .ToListAsync();

Performance Comparison

Approach	Data Transferred	Memory Usage	Performance
Without ProjectTo	All 20 columns	High	❌ Slower
With ProjectTo	Only 5 needed columns	Low	✅ Faster

Best Practice: Always use ProjectTo when working with Entity Framework Core and IQueryable for better performance!

← Back to Examples