CODEWITHSUNDEEP
.netlinqlistsorting
RickyTad
RickyTad

Reputation: 371

Use linq to compare lists of objects

I have several lists with elements of same type, for instance List

class ClassSample
{
  int param1;
  int param2;
  public ClassSample(int par1, int par2) {
    param1 = par1;
    param2 = par2;
  }
}

List<ClassSample> list1 = new List<ClassSample>();
List<ClassSample> list2 = new List<ClassSample>();
List<ClassSample> list3 = new List<ClassSample>();

list1.Add(new ClassSample(2, 3));
list1.Add(new ClassSample(4, 2));

list2.Add(new ClassSample(3, 4));
list2.Add(new ClassSample(4, 6));
list2.Add(new ClassSample(2, 2));
list2.Add(new ClassSample(5, 3));

list3.Add(new ClassSample(4, 2));
list3.Add(new ClassSample(7, 3));
list3.Add(new ClassSample(4, 4));

For the ClassSample class I want to define different functions to get a ranking of an object having that type. For instance

long GetRankByProduct(ClassSample obj) {
   return obj.param1 * obj.param2;
}

long GetRankBySum(ClassSample obj) {
   return obj.param1 + obj.param2;
}

and so on.

I would like to sort the 3 lists by using different dynamical criteria, in form of functions that take as parameters a list of ClassSample objects and a ranking function for ClassSample.

// pseudo-code
public long GetListRankByMax(List<ClassSample> csList, Function<ClassSample, long> rankFunct) {
  long max = csList.Max(x => rankFunct(x));
  return max;
}
public long GetListRankByMin(List<ClassSample> csList, Function<ClassSample, long> rankFunct) {
  long min = csList.Min(x => rankFunct(x));
  return min;
}

public long GetListRankBySum(List<ClassSample> csList, Function<ClassSample, long> rankFunct) {
  long sum = 0;
  foreach (var cs in csList)
      sum += rankFunct(cs);
  return sum;
}

How would a code look like, where the 3 lists are sorted dynamically with different criteria, by passing dynamically the function for the "list ranking" and give it as parameter the function that calculates the "element ranking" ? (for instance to sort the list with the "ByMax" function and by applying to each list element the "ByProduct" ranking function, or whatever other combination).

I actually want to sort the 3 lists (and not the list elements), by using different criteria. For instance if the ClassSample list is inside a container class :

class ContainerClassSample {
    List<ClassSample> ClsList {get;set;}
}

List<ContainerClassSample> containerList = new List<ContainerClassSample>();
ContainerClassSample container1 = new ContainerClassSample { ClsList = list1 };
ContainerClassSample container2 = new ContainerClassSample { ClsList = list2 };
ContainerClassSample container3 = new ContainerClassSample { ClsList = list3 };
containerList.Add(container1);
containerList.Add(container2);
containerList.Add(container3);

I need something like this (I should be able to change dynamically the two functions):

// pseudo-code
var result = containerList.OrderBy(GetListRankByMax, GetRankByProduct); // ??

Upvotes: 1

Views: 72

Answers (1)

paparazzo
paparazzo

Reputation: 45096

why are you making this so hard 

class ClassSample
{
  int param1;
  int param2;
  public int Prod { get { return param1 * param1; } }
  public int Sum { get { return param1 * param1; } }
  public ClassSample(int par1, int par2) {
    param1 = par1;
    param2 = par2;
  }
}

var sortedList = list2.OrderBy(x => x.Sum);

var MinProd = (from x in list2 select x.Prod).Min();

You can pass an IComparer to a Sort

You class can implement IComparable in a class

You are tying to reinvent stuff the framework already does

Upvotes: 1

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