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How to: Sort Arrays Using Custom Criteria

To sort arrays containing simple intrinsic types, you can simply call the Array::Sort method, but to sort arrays containing complex types or to override the default sort criteria, you can override the IComparable::CompareTo method.

In the following example, a structure called Element is derived from IComparable, and written to provide a CompareTo method that uses the average of two integers as the sort criteria.

Example

using namespace System;

value struct Element : public IComparable {
   int v1, v2;

   int CompareTo(Object^ obj) {
      Element^ o = dynamic_cast<Element^>(obj);
      if (o) {
         int thisAverage = (v1 + v2) / 2;
         int thatAverage = (o->v1 + o->v2) / 2;
         if (thisAverage < thatAverage)
            return -1;
         else if (thisAverage > thatAverage)
            return 1;
         return 0;
         }
      else
         throw new ArgumentException
      ("Object must be of type 'Element'");
   }
};

int main() {
   array<Element>^ a = gcnew array<Element>(10);
   Random^ r = new Random;

   for (int i=0; i < a->Length; i++) {
      a[i].v1 = r->Next() % 100;
      a[i].v2 = r->Next() % 100;
   }

   Array::Sort( a );
   for (int i=0; i < a->Length; i++) {
      int v1 = a[i].v1;
      int v2 = a[i].v2;
      int v = (v1 + v2) / 2;
      Console::WriteLine("{0}  (({1}+{2})/2) ", v, v1, v2);
   }
}

See Also

Reference

Array Class

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