Question

我有一个清单，即

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

在以下代码中使用：

var d = new List<Tuple<string, double>>();
            while ((line = file.ReadLine()) != null)
            {
                d.Add(Tuple.Create(line, p.calculate_CS(line, document)));
            }


            System.IO.StreamWriter fileW = new System.IO.StreamWriter(@"C:\Users\Malik\Desktop\write_research_fields_temp.txt");

            foreach (var item in d.OrderByDescending(t => t.Item2))
            {
                fileW.WriteLine("{0} - {1}", item.Item2, item.Item1);

            }

我想在字符串中存储排序（降序）List的第一个元素（只有字符串值而不是double值），即string top_value

任何建议都非常感谢。感谢

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

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

            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);
            }

这是将数据插入数据库的插入方法。

static void write_To_Database(string document, string research_field)
        {
            try
            {
                SqlConnection con = new SqlConnection("Data Source=KHIZER;Initial Catalog=subset_aminer;Integrated Security=True;");

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

                SqlDataReader reader = query.ExecuteReader();


                reader.Read();
                int id = reader.GetInt32(0);
                //reader.Close();

                query.Parameters.Add("@research_field", SqlDbType.Text);
                query.Parameters.Add("@id", SqlDbType.Int);

                query.CommandText = "insert into sub_aminer_paper (research_area) values(@research_field) where id = @id";
                query.ExecuteNonQuery();


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

            }
        }

有什么建议吗？

Answer 1

只需使用一点LINQ对集合进行排序并获取所需的结果。

按您的数值（最大值）排序，然后抓取与之配对的第一个字符串值：

string top_value = d.OrderByDescending(x => x.Item2)
                    .Select(x => x.Item1)
                    .FirstOrDefault();

在你现有的代码中，没有必要遍历所有结果只是为了得到第一个，所以你基本上可以做这样的事情：

foreach (var item in d.OrderByDescending(t => t.Item2))
{
    string top_value = item.Item1;
    ... // do stuff
    break;
}

但那有点傻，所以你可以消除循环：

var orderedItems = d.OrderByDescending(t => t.Item2);
var largestItem = d.FirstOrDefault();  // covers the case where the list is empty

string top_value = largestItem != null ? largestItem.Item1 : null;

我个人更喜欢LINQ，但是YMMV。：）

至于将其存储在数据库中，看起来在创建元组时会丢失document的值。我只是更改了Tuple来存储文档，并稍微修改LINQ语句：

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

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

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

if (top_value != null)
{
    // look up record using top_value.Item3, and then store top_value.Item1
}

如何从Tupled List中获取第一个元素

1 个答案: