Question

I have a List where element is:

struct element { 
                double priority; 
                int value; 
               }

How can I implement my own comparer which allow me sort List by priority ? I try with SortredList… but it don’t allow douplicated keys 🙁

Big thanks for help!

Answer 1

If you can’t rely on C# 3 extensions or Lambdas then you can have your struct implement the IComparable interface, like so:

struct element : IComparable
{
    double priority;
    int value;
    public element(int val, double prio)
    {
        priority = prio;
        value = val;
    }
    #region IComparable Members

    public int CompareTo(object obj)
    {
        // throws exception if type is wrong
        element other = (element)obj;
        return priority.CompareTo(other.priority);
    }

    #endregion
}

There are also a typesafe version of this interface, but the principle is the same

After you have that interface implemented on your struct or class, calling the Sort method on List<> will “just work”

static void Main(string[] args)
{
    Random r = new Random();
    List<element> myList = new List<element>();
    for (int i = 0; i < 10; i++)
        myList.Add(new element(r.Next(), r.NextDouble()));
    // List is now unsorted 
    myList.Sort();
    // List is now sorted by priority
    Console.ReadLine();
}