将两个数据表中的值相加到一个新的数据表中

Question

我有两个强类型数据表（dt1）：

|FirstName|LastName|Val1|Val2|
|Tony     |Stark   |34  |35  |
|Steve    |Rogers  |12  |23  |
|Natasha  |Romanoff|2   |100 |

第二个 (dt2)

|FirstName|LastName|Val1|Val2|
|Tony     |Stark   |16  |5   |
|Bruce    |Banner  |2   |1   |
|Steve    |Rogers  |54  |40  |

我尝试创建一个新的数据表，在其中添加人员的值。我需要一个外部联接，因为我需要所有人，并且第二个表中的值减半。

所以结果应该是这样的：

|FirstName|LastName|Val1|Val2|
|Tony     |Stark   |42  |37.5|
|Steve    |Rogers  |39  |43  |
|Natasha  |Romanoff|2   |100 |
|Bruce    |Banner  |1   |0.5 |

我的方法是使用 LINQ：

Dim query = 
from a in ds1.Table1
Join b in ds2.Table2
On a.FirstName + a.LastName Equals b.FirstName + b.Lastname
Select New With {
.FirstName = a.FirstName,
.LastName = a.LastName,
.Val1 = a.Val1 + b.Val1 *0.5,
.Val2 = a.Val2 + b.Val2 *0.5
}

但我并没有让所有人都接受这种方法。我也试过了

Dim query = 
From a in ds1.Table1
From b in ds2.Table2
Select New With{
Key .KeyName = a.FirstName + a.LastName = b.FirstName + b.FirstName,
.Val1 = a.Val1 + b.Val1 *0.5,
.Val2 = a.Val2 + b.Val2 * 0.5
}

现在每个人都有很多条目。谁能帮我完成这件事。我不知道是否有没有 Linq 的另一种方法来解决这个问题。

Answer 1

使用group by 的示例。要考虑的是在执行group by 和Sum 操作之前，第二个表中的所有值都必须除以2。我在.Concat 之前处理了这个

var dt1 = new List<MyClass>();
dt1.Add(new MyClass { FirstName = "Tony", LastName = "Stark", Val1 = 34, Val2 = 35});
dt1.Add(new MyClass { FirstName = "Steve", LastName = "Rogers", Val1 = 12, Val2 = 23});
dt1.Add(new MyClass { FirstName = "Natasha", LastName = "Romanoff", Val1 = 2, Val2 = 100 });


var dt2 = new List<MyClass>();
dt2.Add(new MyClass { FirstName = "Tony", LastName = "Stark", Val1 = 16, Val2 = 5 });
dt2.Add(new MyClass { FirstName = "Bruce", LastName = "Banner", Val1 = 2, Val2 = 1 });
dt2.Add(new MyClass { FirstName = "Steve", LastName = "Rogers", Val1 = 54, Val2 = 40 });


var q = from a in dt1
                .Concat(
                    from b in dt2 
                    select new MyClass 
                        {
                            FirstName = b.FirstName,
                            LastName = b.LastName,
                            Val1 = b.Val1 * 0.5m,
                            Val2 = b.Val2 * 0.5m
                        })
        group a by new {a.FirstName, a.LastName}
        into g
        select new
            {
                g.First().FirstName,
                g.First().LastName,
                Val1 = g.Sum(x => x.Val1),
                Val2 = g.Sum(x => x.Val2),
            };


foreach (var s in q)
{
    Console.WriteLine("{0} {1} {2} {3}", s.FirstName,s.LastName,s.Val1,s.Val2);
}

结果

Tony Stark 42,0 37,5
Steve Rogers 39,0 43,0
Natasha Romanoff 2 100
Bruce Banner 1,0 0,5

Answer 2

我现在明白了。我的解决方案是：

Dim qLeft = From a in dt1.Getdt1Info
                Group Join b in dt2.Getdt2Info
                On a.FirstName + a.LastName Equals b.FirstName + b.LastName  
                Into NewGroup = Group
                From c in NewGroup.DefaultIfEmpty
                Select New With{
                .Name = a.FirstName + ", " + a.LastName,
                .Value1 = a.Val1 + If (c is nothing, 0D, c.Val1) * 0.5,
                .Value2 = a.Val2 + If (c is nothing, 0D, c.Val2) * 0.5      
                }

Dim qRight =From a in dt2.Getdt2Info
                Group Join b in dt1.Getdt1Info  
                On a.FirstName + a.LastName Equals b.FirstName + b.LastName
                Into NewGroup = Group
                From c in NewGroup.DefaultIfEmpty
                Select New With{
                .Name = a.FirstName + ", " + a.LastName,
                .Value1 = a.val1 * 0.5 + If (c Is Nothing, 0D, c.Val1),
                .Value2 = a.val2 * 0.5 + If (c Is Nothing, 0d, c.Val2)}

Dim qFull = qleft.Concat(qRight).GroupBy(function(x) x.Name).Select(function(x) x.First)

我仍然不知道为什么 qleft.Union(qRight) 不能消除重复项。我用函数（代码）解决了这个问题。