LINQ 使用 C# 将几列交换到 DataTable 的行

Question

我有数据表：

location    Quarter   ppl_required   ppl_available
BLR          Q1        70             35
BLR          Q2        50             45
BLR          Q3        25             28
BLR          Q4        60             58
CHN          Q1        77             92
CHN          Q2        42             66
CHN          Q3        29             20
CHN          Q4        22             24

有没有更好的方法可以使用LINQ 或使用LINQ 的高级功能以非常简单或简短的方式[无循环] 将以下DataTable 输出为.NET3.5 /4.0/4.5 框架。

Location  ppl_Required_Q1  ppl_Required_Q2  ppl_Required_Q3  ppl_Required_Q4  ppl_available_Q1  ppl_available_Q2  ppl_available_Q3  ppl_available_Q4
BLR       70               50               25               60               35                45                28                58
CHN       77               42               29               22               92                66                20                24

Answer 1

我创建了一个与您在 LINQPad 中描述的类似的数据结构，这是我拥有的代码

void Main()
{
    List<Location> locations = new List<Location>
   {
      new Location { Key = "BLR", Quarter = "Q1", PeopleRequired = 70, PeopleAvailable = 35 },
      new Location { Key = "BLR", Quarter = "Q2", PeopleRequired = 50, PeopleAvailable = 45 },
      new Location { Key = "BLR", Quarter = "Q3", PeopleRequired = 25, PeopleAvailable = 28 },
      new Location { Key = "BLR", Quarter = "Q4", PeopleRequired = 60, PeopleAvailable = 58 },
      new Location { Key = "CHN", Quarter = "Q1", PeopleRequired = 77, PeopleAvailable = 92 },
      new Location { Key = "CHN", Quarter = "Q2", PeopleRequired = 42, PeopleAvailable = 66 },
      new Location { Key = "CHN", Quarter = "Q3", PeopleRequired = 29, PeopleAvailable = 20 },
      new Location { Key = "CHN", Quarter = "Q4", PeopleRequired = 22, PeopleAvailable = 24 },
      new Location { Key = "CAD", Quarter = "Q1", PeopleRequired = 100, PeopleAvailable = 150 },
      new Location { Key = "CAD", Quarter = "Q2", PeopleRequired = 200, PeopleAvailable = 250 },
   };

   var results =
   (
      from loc in locations.Select(l => new { l.Key }).Distinct()
      join q1 in locations.Where(l => l.Quarter == "Q1") on loc.Key equals q1.Key into quarter1
      join q2 in locations.Where(l => l.Quarter == "Q2") on loc.Key equals q2.Key into quarter2
      join q3 in locations.Where(l => l.Quarter == "Q3") on loc.Key equals q3.Key into quarter3
      join q4 in locations.Where(l => l.Quarter == "Q4") on loc.Key equals q4.Key into quarter4
      from q1 in quarter1.DefaultIfEmpty()
      from q2 in quarter2.DefaultIfEmpty()
      from q3 in quarter3.DefaultIfEmpty()
      from q4 in quarter4.DefaultIfEmpty()
      select new
      {
         loc.Key,
         Q1_PeopleRequired  = q1 != null ? q1.PeopleRequired  : -1,
         Q1_PeopleAvailable = q1 != null ? q1.PeopleAvailable : -1,
         Q2_PeopleRequired  = q2 != null ? q2.PeopleRequired  : -1,
         Q2_PeopleAvailable = q2 != null ? q2.PeopleAvailable : -1,
         Q3_PeopleRequired  = q3 != null ? q3.PeopleRequired  : -1,
         Q3_PeopleAvailable = q3 != null ? q3.PeopleAvailable : -1,
         Q4_PeopleRequired  = q4 != null ? q4.PeopleRequired  : -1,
         Q4_PeopleAvailable = q4 != null ? q4.PeopleAvailable : -1
      }
   );

   results.Dump();
}

// Define other methods and classes here
public class Location
{
   public string Key          { get; set; }
   public string Quarter      { get; set; }
   public int PeopleRequired  { get; set; }
   public int PeopleAvailable { get; set; }
}

我最终得到的结果就是你想要的。以上可能是也可能不是最好的方法，我在一张大桌子上滞后，但它有效:)

Key | Q1_PeopleRequired | Q1_PeopleAvailable | Q2_PeopleRequired | Q2_PeopleAvailable | Q3_PeopleRequired | Q3_PeopleAvailable | Q4_PeopleRequired | Q4_PeopleAvailable 
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
BLR | 70                | 35                 | 50                | 45                 | 25                | 28                 | 60                | 58
CHN | 77                | 92                 | 42                | 66                 | 29                | 20                 | 22                | 24
CAD | 100               | 150                | 200               | 250                | -1                | -1                 | -1                | -1

Answer 2

我不确定您尝试了什么，是否有任何效率或灵活性需求，或者您对输出容器真正需要什么，但也许像这样简单的东西很有用。假设 dt 是您的数据表：

var newSet = dt.AsEnumerable()
               .GroupBy(r => r.Field<string>("Location"))
               .Select(g => new
               {
                    Location = g.Key,
                    ppl_required_Q1 = g.Where(p => p.Field<string>("Quarter") == "Q1").Sum(p => p.Field<int>("ppl_required")),
                    ppl_required_Q2 = g.Where(p => p.Field<string>("Quarter") == "Q2").Sum(p => p.Field<int>("ppl_required")),
                    ppl_required_Q3 = g.Where(p => p.Field<string>("Quarter") == "Q3").Sum(p => p.Field<int>("ppl_required")),
                    ppl_required_Q4 = g.Where(p => p.Field<string>("Quarter") == "Q4").Sum(p => p.Field<int>("ppl_required")),
                    ppl_available_Q1 = g.Where(p => p.Field<string>("Quarter") == "Q1").Sum(p => p.Field<int>("ppl_available")),
                    ppl_available_Q2 = g.Where(p => p.Field<string>("Quarter") == "Q2").Sum(p => p.Field<int>("ppl_available")),
                    ppl_available_Q3 = g.Where(p => p.Field<string>("Quarter") == "Q3").Sum(p => p.Field<int>("ppl_available")),
                    ppl_available_Q4 = g.Where(p => p.Field<string>("Quarter") == "Q4").Sum(p => p.Field<int>("ppl_available")),
                });

编辑

添加由示例here 和here 组装而成的扩展方法，以防将来链接损坏。您应该可以根据需要进行修改。

public static DataTable ToDataTable<T>(this IEnumerable<T> source, string newTableName)
{
    DataTable newTable = new DataTable(newTableName);

    T firstRow = source.FirstOrDefault();
    if (firstRow != null)
    {
        PropertyInfo[] properties = firstRow.GetType().GetProperties();
        foreach (PropertyInfo prop in properties)
        {
            newTable.Columns.Add(prop.Name, prop.PropertyType);
        }

        foreach (T element in source)
        {
            DataRow newRow = newTable.NewRow();
            foreach (PropertyInfo prop in properties)
            {
                newRow[prop.Name] = prop.GetValue(element, null);
            }
            newTable.Rows.Add(newRow);
        }
    }
    return newTable;
}