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How to convert the below to Async Call

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User-1188570427 posted

How would I convert this to an ASYNC call?

public class Foo
{
    public int Id { get; set; }
    public int? ParentId { get; set; }  
    // other props
}

You can get children of one item using:

List<Foo> GetChildren(List<Foo> foos, int id)
{
    return foos
        .Where(x => x.ParentId == id)
        .Union(foos.Where(x => x.ParentId == id)
            .SelectMany(y => GetChildren(foos, y.Id))
        ).ToList();
}

For ex.

List<Foo> foos = new List<Foo>();

foos.Add(new Foo { Id = 1 });
foos.Add(new Foo { Id = 2, ParentId = 1 });
foos.Add(new Foo { Id = 3, ParentId = 2 });
foos.Add(new Foo { Id = 4 });

GetChild(foos, 1).Dump(); // will give you 2 and 3 (ids)

Tuesday, April 3, 2018 8:30 PM

Answers

User1400794712 posted

Hi tvb2727,

If you want to call GetChildren() asynchronously, you can use async-await for it.

async Task<List<Foo>> GetChildren(List<Foo> foos, int id)
{     
    var re = await foos.AsQueryable() 
        .Where(x => x.ParentId == id)
        .Union(foos.Where(x => x.ParentId == id)
            .SelectMany(y => GetChildren(foos, y.Id).Result)
        ).ToListAsync() ;
    return re;
}

If you want to call this method in MVC controller, we should also add async for the action:

public async Task<ActionResult> LinqTask()
{
    List<Foo> foos = new List<Foo>();

    foos.Add(new Foo { Id = 1 });
    foos.Add(new Foo { Id = 2, ParentId = 1 });
    foos.Add(new Foo { Id = 3, ParentId = 2 });
    foos.Add(new Foo { Id = 4 });

    var list = await GetChildren(foos, 1);
    return View();
}

Best Regards,

Daisy

Marked as answer by Anonymous Thursday, October 7, 2021 12:00 AM

Wednesday, April 4, 2018 3:20 AM

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How to convert the below to Async Call

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