Question

我有以下表结构：

tempDt

col1 = Product (Integer)  
col2 = Customer (Integer)  
col3 = Center (Integer)  
col4 = Date (Date)  
col5 = Price (Double)  
col6 = Sales (Double)

此示例行：

1;1;1;01.01.2012;4.39;20000  
1;1;1;02.02.2012;4.46;15000  
1;1;1;03.03.2012;4.22;25000

以下Linq查询：

For Each item In From u In tempDT.AsEnumerable
Group u By Product = u("Product"), Customer = u("Customer"), Center = u("Center") Into Group
Select Product, Customer, Center, Price = Group.Average(Function(g) g("Price")), Sales = Math.Round(Group.Sum(Function(g) CDbl(g("Sales"))), 2)

tmpDt.Rows.Add(item.Product, item.Customer, item.Center, item.Price, item.Sales)
Next

但结果我得到以下一行： 1; 1; 1; 4.0; 60000

Group.Average截断“价格”栏，出了什么问题？

Answer 1

我不清楚在编译时它不知道类型会选择哪个重载。你可以尝试：

Group.Average(Function(g) g.Field(Of Double)("Price"))

如果这没有帮助，你应该仔细检查在进入LINQ查询之前确实没有截断值，例如：填写数据表时。

Answer 2

您的查询相当难以理解，请查看我的更改（例如，使用强类型DataRow.Field扩展方法）：

Dim groups = From u In tempDT.AsEnumerable
             Group u By Key = New With {
                 .Product = u.Field(Of Integer)("Product"),
                 .Customer = u.Field(Of Integer)("Customer"),
                 .Center = u.Field(Of Integer)("Center")
             } Into PCCroup = Group
             Select New With {
                 .PCC = Key,
                 .Price = PCCroup.Average(Function(u) u.Field(Of Double)("Price")),
                 .Sales = Math.Round(PCCroup.Average(Function(u) u.Field(Of Double)("Sales")), 2)
             }

For Each item In groups
    tmpDt.Rows.Add(item.PCC.Product, item.PCC.Customer, item.PCC.Center, item.Price, item.Sales)
Next

LinQ Group.Average会截断我的值

2 个答案: