namespace _10_4
{
    internal class Program
    {
        static void Main(string[] args)
        {
            string text = @"The quick brown fox jumps over the lazy dog." +
                          @"An apple a day keeps the doctor away." +
                          @"Can a fox and a dog be friends?";
            Console.WriteLine(text);
            string searchTerm = "the";
            string[] source = text.ToLower().Split(new char[] { '.', ' ','!','?','.' }, StringSplitOptions.RemoveEmptyEntries);
            int wordCount = 0;
            foreach (string s in source)
            {
                if (s.CompareTo(searchTerm)==0)
                {
                    wordCount++;
                }
            }
            Console.WriteLine("单词{0}一共出现{1}次，频率{2:#0.##%}",searchTerm,wordCount,wordCount/(double)source.Length);
        }
    }
}