CODEWITHSUNDEEP
c#linq
DDiVita
DDiVita

Reputation: 4265

converting multiple LINQ queries into 1?

Is it possible to convert this code into one LINQ query. I could have sworn I had done something like this before, but I cannot figure out where I might that code might be. I want to perform a sub query and modify the values of the selected items if one list has values from another.

var selectInstructors = _instructorService.GetAllNonGuestInstructors()
                                          .Select(i => new SelectListItem()
                                                       {
                                                           Text = i.User.ToFullName(),
                                                           Value = i.Id.ToString() 
                                                       }).ToList();

var selectedItems = schedule.Instructors
                        .Select(instructior1 => selectInstructors.FirstOrDefault(s => s.Value == instructior1.Id.ToString()))
                        .Where(selectedItem => selectedItem != null);

foreach (var selectedItem in selectedItems )
{
    selectInstructors.Remove(selectedItem);
    selectedItem.Selected = true;
    selectInstructors.Add(selectedItem);
}

So let's assume in the selectInstructors list I have these values: John Smith, 1 Jane Doe, 2 Dave Ritter, 3 (before we iterate the persisted instructors the selected Boolean value is a default of false)

The schedule.Instructors class has the persisted list of instructors for that schedule: John Smith, 1 Dave Ritter, 3

Now, what I would like to do is set any of the Selected properties in selectInstructors where the value is equal to schedule.Instructors

Upvotes: 0

Views: 137

Answers (2)

Risky Martin
Risky Martin

Reputation: 2531

var selectedIds = schedule.Instructors.Select(i => i.Id.ToString()).ToList();    

var instructors = (from instructor in _instructorService.GetAllNonGuestInstructors()
                   let value = instructor.Id.ToString()
                   select new SelectListItem()
                   {
                       Text = instructor.User.ToFullName(),
                       Value = value,
                       Selected = selectedIds.Contains(value)
                   }).ToList();

Upvotes: 2

yo chauhan
yo chauhan

Reputation: 12315

            var allInstructors = _instructorService.GetAllNonGuestInstructors();
        if(allInstructors!=null)
            allInstructors.Select(i =>
                    new SelectListItem() { Text = i.User.ToFullName(), Value = i.Id.ToString() }).
                    Zip(schedule.Instructors,(selectedItems,instructor)=>
                    {var item = selectedItems.FirstOrDefault(s => s.Value == instructior.Id.ToString());
                        if(item!=null)
                            item.Selected=true;});
      //Now use allInstructors collection further it will have Selected true according to your conditions.

I can't understand one thing why selectedItem is removed and then added. Anyways I hope this will help.

Upvotes: 1

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