Question

有人可以用linq查询帮助我获得以下结果集吗？

首先是DInfo

ID  DId DName
1   D1  DName1
2   D2  DName2
3   D3  Dname3

第二个是MInfo

ID  DId MId MName
1   D1  1   MName1
2   D1  2   MName2
3   D2  1   MName3
4   D2  2   MName4
5   D2  3   MName5

第三是VData（交易表）

ID  Did Mid Value   DateTime
1   D1  1   10.25   2018-04-15 17:33:22
2   D1  1   11.26   2018-04-15 19:33:22
3   D1  1   12.30   2018-04-15 22:33:22
4   D1  2   45.50   2018-04-15 17:33:22
5   D1  2   50.40   2018-04-15 19:33:22
6   D1  2   60.66   2018-04-15 22:33:22
6   D2  1   60.41   2018-04-15 19:33:22
7   D2  1   66.22   2018-04-15 22:33:22
8   D2  1   70.65   2018-04-15 23:33:22

我对结果集的想法是从DInfo获取所有不同的行，并从MInfo查找与DInfo的DID匹配的所有行，然后为每个唯一行从事务表中获取第一个和最后一个值（基于日期时间）

我期望的ResultSet如下

MName   OpeningValue    ClosingValue
MName1  10.25            12.30
MName2  45.50            60.66
MName3  60.41            70.65

以上数据仅供参考，实际上在生产场景中可能会有所不同。所有表中的行数。

谢谢

Answer 1

尝试关注：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;


namespace ConsoleApplication108
{
    class Program
    {
        static void Main(string[] args)
        {
            DataTable mInfo = new DataTable();
            mInfo.Columns.Add("ID", typeof(int));
            mInfo.Columns.Add("Did", typeof(string));
            mInfo.Columns.Add("Mid", typeof(int));
            mInfo.Columns.Add("MName", typeof(string));

            mInfo.Rows.Add(new object[] {1, "D1", 1, "MName1"});
            mInfo.Rows.Add(new object[] {2, "D1", 2, "MName2"});
            mInfo.Rows.Add(new object[] {3, "D2", 1, "MName3"});
            mInfo.Rows.Add(new object[] {4, "D2", 2, "MName4"});
            mInfo.Rows.Add(new object[] {5, "D2", 3, "MName5"});

            DataTable vData = new DataTable();
            vData.Columns.Add("ID", typeof(int));
            vData.Columns.Add("Did", typeof(string));
            vData.Columns.Add("Mid", typeof(int));
            vData.Columns.Add("Value", typeof(decimal));
            vData.Columns.Add("DateTime", typeof(DateTime));

            vData.Rows.Add(new object[] { 1, "D1", 1, 10.25, DateTime.Parse("2018-04-15 17:33:22")});
            vData.Rows.Add(new object[] { 2, "D1", 2, 11.26, DateTime.Parse("2018-04-15 19:33:22")});
            vData.Rows.Add(new object[] { 3, "D2", 1, 12.30, DateTime.Parse("2018-04-15 22:33:22")});
            vData.Rows.Add(new object[] { 4, "D2", 2, 45.50, DateTime.Parse("2018-04-15 17:33:22")});
            vData.Rows.Add(new object[] { 5, "D2", 3, 50.40, DateTime.Parse("2018-04-15 19:33:22")});
            vData.Rows.Add(new object[] { 6, "D1", 2, 60.66, DateTime.Parse("2018-04-15 22:33:22")});
            vData.Rows.Add(new object[] { 6, "D2", 1, 60.41, DateTime.Parse("2018-04-15 19:33:22")});
            vData.Rows.Add(new object[] { 7, "D2", 1, 66.22, DateTime.Parse("2018-04-15 22:33:22")});
            vData.Rows.Add(new object[] { 8, "D2", 1, 70.65, DateTime.Parse("2018-04-15 23:33:22")});

            var results = vData.AsEnumerable().OrderBy(x => x.Field<DateTime>("DateTime"))
                .GroupBy(x => new { Did = x.Field<string>("Did"), Mid = x.Field<int>("Mid") })
                .Select(x => new
                {
                    MName = mInfo.AsEnumerable().Where(y => (y.Field<string>("Did") == x.Key.Did) && (y.Field<int>("Mid") == x.Key.Mid)).FirstOrDefault().Field<string>("MName"),
                    OpeningValue = x.First().Field<decimal>("Value"),
                    ClosingValue = x.Last().Field<decimal>("Value")
                }).ToList();

        }
    }

}

Linq查询复杂结果集

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