C# Generics Sample

Generics provide the tool to create flexible reusable code by allowing classes, structures, interfaces, methods and delegates to be declared as a generic type instead of an actual type; the actual type is specified later. The System.Collections.Generic namespace provides generic collection classes that make creating type safe collections very easy.

In this example we focus on the type safe collection classes and show how their type safety works and what the speed benefit is of using a generic collection over a standard collection.

This sample requires the following to be installed: Visual Studio 2008. You can checkout a read-only copy of this sample using tortoise from:
http://bakopanos.googlecode.com/svn/trunk/csharpsamples/GenericSamples/ComparableConstraint

using System;
using System.Collections.Generic;

namespace ComparableConstraint
{
    interface IPriorityQueue<TE, TP> where TP : IComparable<TP>
    {
        //
        void Put(TE element, TP priority);
        //
        TE Get();
        //
        int Count { get;}       
    }
    
    class PriorityQueue<TE, TP> : IPriorityQueue<TE, TP>
    where TP : IComparable<TP>
    {
        struct KeyValuePair<TK, TV>
        {
            public readonly TK Key;
            public readonly TV Value;

            public KeyValuePair(TK key, TV value)
            {
                Key = key;
                Value = value;
            }
        }

        readonly List<KeyValuePair<TP, TE>> _list = new List<KeyValuePair<TP, TE>>();

        public void Put(TE element, TP priority) { 
          _list.Add(new KeyValuePair<TP,TE>(priority, element));
        }

        public TE Get()
        {
            int maxInd = 0;
            for (int i = 0; i < _list.Count; i++)
            {
                if (_list[i].Key.CompareTo(_list[maxInd].Key) > 0)
                    maxInd = i;
            }
            TE val = _list[maxInd].Value;
            _list.RemoveAt(maxInd);
            return val ;
        }

        public int Count { get { return _list.Count; }}
    }

    class Program
    {
        static void Main()
        {
            IPriorityQueue<String, int> pq1 = new PriorityQueue<String, int>();    //ok
            pq1.Put("String 1 mit Prio 7", 7);
            pq1.Put("String 2 mit Prio 4", 4);
            pq1.Put("String 3 mit Prio 1", 1);
            pq1.Put("String 4 mit Prio 5", 5);

            while (pq1.Count > 0)
            {
                string s = pq1.Get();
                Console.WriteLine(s);
            }
            Console.ReadLine();            
        }
    }
}