使用元组列表 c# 执行 while 循环

Question

我有这段代码用于将数据插入数据库。我创建了一个 <string, double, string[]> 的元组列表，并将元素添加到嵌套 while 循环内的列表中。这是代码....

    System.IO.StreamReader file = new System.IO.StreamReader(@"C:\Users\Malik\Desktop\research_fields.txt");


            Program p = new Program();

            var dd = new List<Tuple<string, double, string>>();

            //string document = "The trie data structure has many properties which make it especially attractive for representing large files of data. These properties include fast retrieval time, quick unsuccessful search determination, and finding the longest match to a given identifier. The main drawback is the space requirement. In this paper the concept of trie compaction is formalized. An exact algorithm for optimal trie compaction and three algorithms for approximate trie compaction are given, and an analysis of the three algorithms is done. The analysis indicate that for actual tries, reductions of around 70 percent in the space required by the uncompacted trie can be expected. The quality of the compaction is shown to be insensitive to the number of nodes, while a more relevant parameter is the alphabet size of the key.";

            //string[] document = get_Abstract();
            string line;
            try
            {
                SqlConnection con = new SqlConnection("Data Source=KHIZER;Initial Catalog=subset_aminer;Integrated Security=True");

                con.Open();
                SqlCommand query = con.CreateCommand();
                query.CommandText = "select p_abstract from sub_aminer_paper where pid between 1 and 500 and DATALENGTH(p_abstract) != 0";

                SqlDataReader reader = query.ExecuteReader();

                string summary = null;
                while (reader.Read())
                {
                    summary = reader["p_abstract"].ToString();

                    while ((line = file.ReadLine()) != null)
                    {
                        dd.Add(Tuple.Create(line, p.calculate_CS(line, summary), summary));
                    }

                    var top_value = dd.OrderByDescending(x => x.Item2).FirstOrDefault();

                    if (top_value != null)
                    {
                        // look up record using top_value.Item3, and then store top_value.Item1
                        var abstrct = top_value.Item3.ToString();
                        var r_field = top_value.Item1.ToString();

                        write_To_Database(abstrct, r_field);
                    }
                }

                reader.Close();
 }
            catch (Exception e)
            {
                Console.WriteLine("Exception: " + e.Message);
            }
            finally
            {
                Console.WriteLine("Executing finally block.");

            }

我已经在 Visual Studio 2013 中使用 c# 对其进行了调试，我看到了内部 while 循环内的语句，即 dd.Add(Tuple.Create(line, p.calculate_CS(line, summary), summary)); 只执行一次，而它应该执行 22 次，因为 reader.Read() 的长度为 22 个文档。 我已经通过在代码中仅采用单个string document 显示为//comment 来检查它，它工作正常，但不能从数据库中读取文档。 不明白为什么会这样。任何建议都将受到高度赞赏。

Answer 1

要进入while 循环，您的line = file.ReadLine()) != null 应该为真。如果您只到达那里一次，我怀疑您的文件中只有一行，因此，无论您的 document 数组有多少元素，while 中的代码都只会执行一次。

不过，总的来说，您的 while 循环代码对我来说没有多大意义。您将在for 的第一次迭代中读取文件中的所有文本，然后将永远跳过while 循环。如果您打算只读取所有行一次，请将while 移到for 之前。

要进一步改进您的代码，请查看 ReadLines 和 AddRange 页面。

并在集合中找到最大值而不是

var top_value = dd.OrderByDescending(x => x.Item2).FirstOrDefault();

使用Max:

var top_value = dd.Max(x => x.Item2);

更新：

var lines =  System.IO.File.ReadLines(@"C:\Users\Malik\Desktop\research_fields.txt");
 while (reader.Read())
{
    summary = reader["p_abstract"].ToString();
    dd.AddRange(lines
        .Select( line => 
            Tuple.Create(line, p.calculate_CS(line, summary), summary)
        )
    ); 
    // rest of your stuff
}