async await with Select() in Linq

Question

I have a ViewComponent, and DTO and ViewModel classes. I want to pass a list of ViewModels to the view, but because of async/await I cannot do it in one line like so:

 List<PageVM> pages = await _context.Pages.ToArray().Where(x => x.Slug != "home").OrderBy(x => x.Sorting).Select(x => new PageVM(x)).ToList();

I can do it in more lines like so:

List<PageVM> pages = new List<PageVM>();

List<PageDTO> dto = await _context.Pages.Where(x => x.Slug != "home").ToListAsync();

foreach (var item in dto)
{
    pages.Add(new PageVM(item));
}

But is it possible to modify the one line so it works with await?

Tomas Aschan · Accepted Answer · 2018-06-16 10:36:00Z

2

Yes, it is; note the parentheses:

var pages = (await _context.Pages.Where(x => x.Slug != "home").ToListAsync()).Select(x => new PageVM(x)).ToList();

However, this is equivalent to the following two statements:

var dtos = await _context.Pages.Where(x => x.Slug != "home").ToListAsync();
var pages = dtos.Select(x => new PageVM(x)).ToList();

which IMO is much easier to read.

answered Jun 16, 2018 at 10:36

Tomas Aschan

61.1k62 gold badges266 silver badges423 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Ajay Gupta · Accepted Answer · 2018-06-16 15:27:44Z

0

Yes, you need to wrap the awaited expression with parenthesis. Something like this should do.

List<PageVM> pages = (await _context.Pages.Where(x => x.Slug != "home").ToListAsync())
.Select(item => new PageVM(item)).ToList();

edited Jun 16, 2018 at 15:27

Ajay Gupta

1,8651 gold badge14 silver badges22 bronze badges

answered Jun 16, 2018 at 10:36

zcharles

1906 bronze badges

Collectives™ on Stack Overflow

async await with Select() in Linq

2 Answers 2

Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Related