List & Array (edit)

Algorithms

Intersection of Two Unsorted Arrays

http://www.codinghelmet.com/exercises/array-intersection

http://www.codinghelmet.com/exercises/counting-intersection-of-two-unsorted-arrays

References

Intersection of two arrays in C#

https://stackoverflow.com/questions/20687338/intersection-of-two-int-array-in-c-sharp

https://stackoverflow.com/questions/10866756/fast-intersection-of-two-sorted-integer-arrays

Merge two array

https://stackoverflow.com/questions/59217/merging-two-arrays-in-net?rq=1

Sort dictionary

https://stackoverflow.com/questions/289/how-do-you-sort-a-dictionary-by-value?rq=1

Pass an array of integers to ASP.NET Web API

https://stackoverflow.com/questions/9981330/pass-an-array-of-integers-to-asp-net-web-api?rq=1

EF Core 2.1 select/distinct

var resulat = from a in A
                  join b in B equals a.level=b.level
                  where ...
                  select new M1 {AId = a.id};

    (from r in resulat
    join c in C equals r.AId = c.AId
    select new M2 
    {
      CId = c.Id
      level = c.level
    }).Distinct();

https://stackoverflow.com/questions/54061471/ef-core-2-1-select-distinct

EF Core 2.1

https://entityframeworkcore.com/knowledge-base/51234185/translate-sql-query-into-entity-framework-core-2-1

https://entityframeworkcore.com/knowledge-base/54468767/selecting-all-rows-based-on-a-distinct-column-in-entity-framework-core

Distinct

List<int> ages = new List<int> { 21, 46, 46, 55, 17, 21, 55, 55 };
IEnumerable<int> distinctAges = ages.AsQueryable().Distinct();
Console.WriteLine("Distinct ages:");
foreach (int age in distinctAges)
  Console.WriteLine(age);
/* This code produces the following output: Distinct ages: 21 46 55 17 */

GroupBy Example

var directors = new[] { new { DirectorName = "Director A", DirectorID = 1 },
                        new { DirectorName = "Director B", DirectorID = 2 }};
var movies = new[] { new { MovieName = "Movie A", MovieID = 1, DirectorID = 1 },
                     new { MovieName = "Movie B", MovieID = 2, DirectorID = 2 }};
var actors = new[] { new { ActorName = "Actor A", ActorID = 1, MovieID = 1},
                     new { ActorName = "Actor B", ActorID = 2, MovieID = 1},
                     new { ActorName = "Actor C", ActorID = 3, MovieID = 1},
                     new { ActorName = "Actor D", ActorID = 4, MovieID = 2}};

var results = from d in directors
              from m in movies
                .Where(m => m.DirectorID == d.DirectorID)
              from a in actors
                .Where(a => a.MovieID == m.MovieID)
              where d.DirectorID == 1
              group new { d, m, a } by d.DirectorName into grp
              select new 
              { DirectorName = grp.Key,
                MovieCount = grp.Select(x => x.m).Distinct().Count(),
                ActorCount = grp.Select(x => x.a).Distinct().Count()
              };

GroupBy

https://stackoverflow.com/questions/57673111/ef-core-2-1-evaluates-locally-when-sum-complex-and-grouping?rq=1

return query
   .GroupBy(e => new // Key
   { 
       e.DivisionCode,
       e.DivisionDescription,
       e.TopDivisionCode,
       e.TopDivisionDescription,
       e.PostingDate
   },
   e => new // Element
   {
       e.LineAmount,
       RUCAmount = e.LineAmount - (e.Quantity * e.UnitCostLcy) // <--
   })
  .Select(g => new V_TurnoverByDivision
  {
      DivisionCode = g.Key.DivisionCode,
      DivisionDescription = g.Key.DivisionDescription,
      TopDivisionCode = g.Key.TopDivisionCode,
      TopDivisionDescription = g.Key.TopDivisionDescription,
      PostingDate = g.Key.PostingDate,
      LineAmount = g.Sum(e => e.LineAmount),
      RUCAmount = g.Sum(e => e.RUCAmount) // <--
  }); 

Entity Framework Core 2.1 How to OrderBy() and Distinct()

return await _context.SdrSettingHistory
    .Where(x => x.StartDate != null)
    .Select(x => x.StartDate.Value.Year)
    .Distinct()
    .OrderBy(x => x)
    .ToListAsync();

https://stackoverflow.com/questions/52677846/entity-framework-core-2-1-how-to-orderby-and-distinct

Programming: Intersect Two Arrays C#

Input: Array 1: [90,95,136,137], Array 2: [95,135,136,137]

Output: Array INTERSECT: [95,136,137], Array DELETE: [90], Array NEW: [135]

static void Main(string[] args)
{
 List<int> lstIDInDB = new List<int>()
 {
   90,95,136,137
 };

 List<int> lstIDInModel = new List<int>()
 {
   95,135,136,137
 };

 //var arrKeep = (from x in lstIDInDB
 // join y in lstIDInModel on x equals y
 // select x)
 // .OrderBy(x => x)
 // .ToList();

 var arrKeep = lstIDInDB.Intersect(lstIDInModel).ToList();

 Console.WriteLine("Items will be Keep:");

 //Keep
 for (int i = 0; i < arrKeep.Count; i++)
 {
 Console.WriteLine(arrKeep[i]);
 }

 //var arrDeleteAll = (from x in lstIDInDB
 // join y in lstIDInModel on x equals y into z
 // from t in z.DefaultIfEmpty()
 // select x)
 // .OrderBy(x => x)
 // .ToList();
 //var arrDelete = arrDeleteAll.Except(arrKeep).ToList();

 var arrDelete = lstIDInDB.Except(arrKeep).ToList();

 Console.WriteLine("Items will be Delete:");
 //Delete
 for (int i = 0; i < arrDelete.Count; i++)
 {
 Console.WriteLine(arrDelete[i]);
 }

 //var arrNewAll = (from x in lstIDInModel
 // join y in lstIDInDB on x equals y into z
 // from t in z.DefaultIfEmpty()
 // select x)
 // .OrderBy(x => x)
 // .ToList();
 //var arrNew = arrNewAll.Except(arrKeep).ToList();

 var arrNew = lstIDInModel.Except(arrKeep).ToList();
 Console.WriteLine("Items will be New:");
 //New
 for (int i = 0; i < arrNew.Count; i++)
 {
 Console.WriteLine(arrNew[i]);
 }
}