The beginnings of an HMM POS tagger for my computational linguistics course

HMMTagger.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
using System.IO;

namespace HMMTagger
{
    class Tuple<T1, T2>
    {
        public T1 Item1 { get; set; }
        public T2 Item2 { get; set; }

        public Tuple(T1 Item1, T2 Item2)
        {
            this.Item1 = Item1;
            this.Item2 = Item2;
        }

        public override bool Equals(object obj)
        {
            if (!(obj is Tuple<T1, T2>))
                return false;

            var t = obj as Tuple<T1, T2>;
            
            return t.Item1.Equals(Item1) && t.Item2.Equals(Item2);
        }

        public override int GetHashCode()
        {
            return Item1.GetHashCode() + Item2.GetHashCode();
        }

        public override string ToString()
        {
            return string.Format("({0}, {1}",
              Item1.ToString(), Item2.ToString());
        }
    }

    class Program
    {
        static Dictionary<Tuple<string, string>, int> categoryFreqs;
        static Dictionary<Tuple<string, string>, int> wordFreqs;

        static void Main(string[] args)
        {
            if (args.Length < 1)
            {
                Console.WriteLine("Usage: {0} [file]", 
                  Path.GetFileName(Assembly.GetExecutingAssembly().Location));
                return;
            }

            FileStream file;
            try
            {
                file = File.OpenRead(args[0]);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                return;
            }

            using (StreamReader reader = new StreamReader(file))
            {
                categoryFreqs = new Dictionary<Tuple<string, string>, int>();
                wordFreqs = new Dictionary<Tuple<string, string>, int>();

                while (!reader.EndOfStream)
                {
                    string line = reader.ReadLine();
                    ProcessLine(line);
                }
            }

            var populars = (from v in wordFreqs orderby v.Value descending select v).Take(10);

            foreach (var p in populars)
                Console.WriteLine("{0} - {1}", p.Key, p.Value);
        }

        static void ProcessLine(string line)
        {
            if (line == "")
                return;

            var words = line.Split(new[] { ' ' });
            var cleanWords = from w in words where w.Contains('/') select w;

            foreach (var w in cleanWords)
            {
                var components = w.Split(new[] { '/' });
                if (components.Length != 2)
                    continue;

                var key = new Tuple<string, string>(components[0], components[1]);
                if (!wordFreqs.ContainsKey(key))
                    wordFreqs.Add(key, 1);
                else
                    ++wordFreqs[key];
            }
        }
    }
}