C#•3y ago

Entityframework .Select vs Mapping method [Answered]

Is the following the same or has it performance difference?

var myList = await _dbContext.SomeList.Select(x => new myDTO{...}.ToListAsync();

var myList = await _dbContext.SomeList.Select(x => new myDTO{...}.ToListAsync();

var myData = await _dbContext.SomeList.ToListAsync();
var myList = MapToMyDTO(myData);

var myData = await _dbContext.SomeList.ToListAsync();
var myList = MapToMyDTO(myData);

4 Replies

ogie1985OP•3y ago

Also which one is prefered more.. ?

Angius•3y ago

The first one will generate SQL that only fetches the necessary data The second one will fetch everything, and map the data afterwards Using .Select() before the query gets resolved will always result in less data being fetched, and fewer memory allocations

Unknown User•3y ago

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Accord•3y ago

✅ This post has been marked as answered!

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Entityframework .Select vs Mapping method [Answered]