C/C++ programs inadvertently free/delete objects which are still in use:

int *p, *q;                 int *p, *q;
p = malloc(sizeof(int));    p = new int;
*p = 27;                    *p = 27;
q = p;                      q = p;
free(p);                    delete p;
printf("%d\n", *q);         cout << *q << endl;

And programs often cause memory leaks by not using free/delete on unwanted objects.

Like Java, in C# you do not delete objects: instead, these languages have garbage collection. The garbage collector detects objects no longer in use, and reuses their space.