使用C# LINQ 查詢字符串中某個詞出現的次數

public static void CountWords()
        {
            string text = @"Historically, the world of data and the world of objects" +
            @" have not been well integrated. Programmers work in C# or Visual Basic" +
            @" and also in SQL or XQuery. On the one side are concepts such as classes," +
            @" objects, fields, inheritance, and .NET Framework APIs. On the other side" +
            @" are tables, columns, rows, nodes, and separate languages for dealing with" +
            @" them. Data types often require translation between the two worlds; there are" +
            @" different standard functions. Because the object world has no notion of query, a" +
            @" query can only be represented as a string without compile-time type checking or" +
            @" IntelliSense support in the IDE. Transferring data from SQL tables or XML trees to" +
            @" objects in memory is often tedious and error-prone.";
            string searchTerm = "data";
            string[] source = text.Split(new char[] { '.', '?', '!', ' ', ';', ':', ',' },
                StringSplitOptions.RemoveEmptyEntries);
            //使用傳統fori循環統計
            int wordCounts = 0;
            for (int i = 0; i < source.Length; i++)
            {
                if (source[i].ToLowerInvariant()==searchTerm.ToLowerInvariant())
                {
                    wordCounts += 1;
                }
            }
            //使用LINQ語句查詢統計
            var matchQuery = from word in source
                             where word.ToUpperInvariant() == searchTerm.ToUpperInvariant()
                             select word;
            int wordCount = matchQuery.Count();
            Console.WriteLine("{0} occurrences(s) of the search term \"{1}\" were found.", wordCounts, searchTerm);
            Console.WriteLine("{0} occurrences(s) of the search term \"{1}\" were found.",wordCount,searchTerm);
            Console.ReadKey();
        }