C#：对键为 List<object> 的字典进行排序

Question

大家好！ Tl;博士我有一个Dictionary<string, List<object>> 叫 具有以下键的“表”：

"id" being int,
"date" being Datetime,
"name", "entry1", "entry2", "entry3" being strings.

以及List<object> 列表中键的所有值。我想通过name 字段订购字典，名称类似于“John Doe”。我尝试使用 .OrderBy() ，它要么抛出异常，要么只订购那个键而不是整个字典。例如：var result = table.Orderby(pairs => pairs.Value[2]); 会抛出异常，因为对象不是字符串。 如何才能做到这一点？谢谢！

编辑： 该表用于使用 Excel 文件中的值：

           foreach (var key in table.Keys)
            {
                for (int i = 0; i < max; i++)
                {
                    switch (key)
                    {
                        case "id":
                            worksheet.Cells[i + 1, j].Value = ConversionWrapper<int>((int)table[key][i]);
                            break;
                        case "date":
                            worksheet.Cells[i + 1, j].Value = ConversionWrapper<string>((DateTime)table[key][i]);
                            break;
                        case "name":
                        case "entry1":
                        case "entry2":
                        case "entry3":
                        case "entry4":
                            worksheet.Cells[i + 1, j].Value = ConversionWrapper<string>((string)table[key][i]);
                            break;
                        default:
                            break;
                    }
                }

                ++j;
            }

       private static T ConversionWrapper<T>(object elem)
        {
            switch (elem)
            {
                case int:
                case string:
                    return (T)elem;
                case DateTime:
                    return (T)(object)((DateTime)elem).ToString("dd/MM/yyyy", CultureInfo.InvariantCulture);
                default:
                    throw new ArgumentException();
            }
        }

Method to extract the values:

        private static Dictionary<string, List<object>> GetAllElementsLM(SqlConnection conn)
        {
            string query;
            string[] columns = { "id", "date", "name", "entry1", "entry2", "entry3", "entry4" };
            var dic = new Dictionary<string, List<object>>();

            conn.Open();

            foreach (var elem in columns)
            {
                dic.Add(elem, new List<object>());

                query = $@"SELECT {elem} FROM ""feedback""";

                using (var command = new SqlCommand(query, conn))
                {
                    using (var reader = command.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            dic[elem].Add(reader.GetValue(0));
                        }
                    }
                }
            }

            conn.Close();

            return dic;
        }

Answer 1

您要排序的类（本例中为列表）需要实现 IComparer 接口。然后 OrderBy 运算符调用 IComparer.Compare 来确定排序顺序。

IComparer.Compare

所以你需要创建一个扩展 List 并实现 IComparer 的类。在此类的比较方法中，您可以执行任何必要的操作来确定哪个列表更大（例如，基于列表中的某个值）。然后，您的字典会将这个新类作为第二种类型。

Answer 2

最终使用了我的结构的List：

条目结构：

readonly struct Entries
    {
        public int Id { get; }
        public DateTime Date { get; }
        public string Name { get; }
        public string Entry1 { get; }
        public string Entry2 { get; }
        public string Entry3 { get; }
        public string Entry4 { get; }

        public Entries(int id, DateTime date, string name, string entry1, string entry2, string entry3, string entry4) =>
                (Id, Date, Name, Entry1, Entry2, Entry3, Entry4) = (id, date, name, entry1, entry2, entry3, entry4);
    }

获取元素个数的方法：

        private static int GetMaxNumber(SqlConnection conn)
        {
            int i = 0;
            string query;

            conn.Open();

            query = $@"SELECT id FROM ""feedback""";

            using (var command = new SqlCommand(query, conn))
            {
                using (var reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        ++i;
                    }
                }
            }

            conn.Close();

            return i;
        }

获取元素：

        private static IEnumerable<Entries> GetAllElementsClass(SqlConnection conn)
        {
            string query;
            List<int> id;
            List<DateTime> date;
            List<string> name, entry1, entry2, entry3, entry4;
            int max = GetMaxNumber(conn);

            conn.Open();

            query = $@"SELECT id FROM ""feedback""";

            id = new List<int>();

            using (var command = new SqlCommand(query, conn))
            {
                using (var reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        id.Add((int)reader.GetValue(0));
                    }
                }
            }

            query = $@"SELECT date FROM ""feedback""";

            date = new List<DateTime>();

            using (var command = new SqlCommand(query, conn))
            {
                using (var reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        date.Add((DateTime)reader.GetValue(0));
                    }
                }
            }

            query = $@"SELECT name FROM ""feedback""";

            name = new List<string>();

            using (var command = new SqlCommand(query, conn))
            {
                using (var reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        name.Add((string)reader.GetValue(0));
                    }
                }
            }

            query = $@"SELECT entry1 FROM ""feedback""";

            entry1 = new List<string>();

            using (var command = new SqlCommand(query, conn))
            {
                using (var reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        entry1.Add((string)reader.GetValue(0));
                    }
                }
            }

            query = $@"SELECT entry2 FROM ""feedback""";

            entry2 = new List<string>();

            using (var command = new SqlCommand(query, conn))
            {
                using (var reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        entry2.Add((string)reader.GetValue(0));
                    }
                }
            }

            query = $@"SELECT entry3 FROM ""feedback""";

            entry3 = new List<string>();

            using (var command = new SqlCommand(query, conn))
            {
                using (var reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        entry3.Add((string)reader.GetValue(0));
                    }
                }
            }

            query = $@"SELECT entry4 FROM ""feedback""";

            entry4 = new List<string>();

            using (var command = new SqlCommand(query, conn))
            {
                using (var reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        entry4.Add((string)reader.GetValue(0));
                    }
                }
            }

            for (int i = 0; i < max; i++)
            {
                yield return new Entries(id[i], date[i], name[i], entry1[i], entry2[i], entry3[i], entry4[i]);
            }

            conn.Close();
        }

对它们进行排序：

        private static List<Entries> SortEntries(SqlConnection conn)
        {
            var entries = new List<Entries>();

            foreach (var element in GetAllElementsClass(conn))
            {
                entries.Add(element);
            }

            entries = entries.OrderBy(x => x.Name).ToList();

            return entries;
        }