LINQ如何根据属性值过滤数据

Question

i have a problem with filtering data in LINQ , here is my Model :

 public class CoursePlan
    {
        [PrimaryKey, AutoIncrement]
        public int Id { get; set; }
        public string Semester { get; set; }
        public string ModuleCode { get; set; }
        public string ModuleName { get; set; }
        public string Credits { get; set; }
        public string OrderNumber { get; set; }
        public string ModuleStatus { get; set; }

    }

and here is my data Json

the problem here some modules having same OrderNumber which mean they are optional , student must study one of them and if student already study one of them , i should ignore other modules in same order number.

in other way to describe the question

i want to return a list of CoursePlan and on this list if there is two items having same OrderNumber check the ModuleStatus for each one of them and if any one is Completed remove other modules on that order otherwise return them all .

here is my code

var coursePlanList = await _sqLiteAsyncConnection.Table<CoursePlan>().ToListAsync();
var groupedData = coursePlanList.OrderBy(e => e.Semester)
    .GroupBy(e => e.OrderNumber)
    .Select(e => new ObservableGroupCollection<string, CoursePlan>(e))
    .ToList();

for now im solving this by this algorithm and not sure if it's the best

    var coursePlanList = await _sqLiteAsyncConnection.Table<CoursePlan>().ToListAsync();

    List<CoursePlan> finalList = new List<CoursePlan>();

    var counter = 0;
    foreach (var itemPlan in coursePlanList)
    {
        if (counter > 0 && counter < coursePlanList.Count)
            if (itemPlan.OrderNumber == coursePlanList[counter - 1].OrderNumber)
            {
                if (itemPlan.ModuleStatus == "Completed")
                {
                    finalList.RemoveAll(a => a.OrderNumber == itemPlan.OrderNumber);
                    finalList.Add(itemPlan);
                }
                Debug.WriteLine(itemPlan.ModuleName + "With -->" + coursePlanList[counter - 1].ModuleName);
            }

            else
                finalList.Add(itemPlan);

        counter++;
    }

    var groupedData = finalList.OrderBy(e => e.ModuleStatus)
        .ThenBy(e => e.Semester)
        .GroupBy(e => e.Semester)
        .Select(e => e)
        .ToList();

    CoursePlanViewList.BindingContext = new ObservableCollection<IGrouping<string, CoursePlan>>(groupedData);

Any advise or guidance would be greatly appreciated

Answer 1

Let me rephrase your requirement: you want to show all plans per OrderNumber that meet the condition: none of the plans in their group should be "Completed" or the plans themselves should be "Completed". All this grouped by Semester :

var plansQuery = 
from p in _sqLiteAsyncConnection.Table<CoursePlan>()
group p by p.Semester into sem
select new
{
    PlansInSemester = 
        from p in sem
        group p by p.OrderNumber into gp
        select new
        {
            PlansInOrderNumber =
                gp.Where(p => !gp.Any(p1 => p1.ModuleStatus == "Completed")
                           || p.ModuleStatus == "Completed")
        }
};

This gives you an IQueryable that produces the course plans you want to select, but grouped in two levels, so the final result is obtained by flattening the query twice:

var coursePlanList = await plansQuery
    .SelectMany(x => x.PlansInSemester
        .SelectMany(y => y.PlansInOrderNumber)).ToListAsync()