Question

我的LINQ查询未生成下面的预期输出。基本上，它是table3.cost对应于table1..code和table2.class的总和，由table1.alias分类并由table1.priority排序。我在DataSet中添加了两个DataRelation：

ds.Relations.Add("Table1Table2", ds.Tables[1].Columns("ID"), ds.Tables[2].Columns("ParentID");
ds.Relations.Add("Table2Table3", 
    new DataColumn[] { ds.Tables[2].Columns["Code"], ds.Tables[2].Columns["Class"] },            
    new DataColumn[] { ds.Tables[3].Columns["Code"], ds.Tables[3].Columns["Class"] });

var query = from aliases in table1.AsEnumerable()
    join children in table2.AsEnumerable() on aliases("ID") equals children("ParentID")
    orderby aliases("priority")
    select new
    {
        Name = aliases("alias"),
        Cost = 
            from data in table3.AsEnumerable()
            group data by new { code = data("code"), classcode = data("class") }
            into datatemp
            select new
            {
                cost = datatemp.Sum(x => x("cost"))
            }
    };

任何想法我做错了什么？提前谢谢！

table1: list of aliases and priorities
-----------------
alias   priority
alias1  1
alias2  2
alias3  4
alias4  3

table2: children records joined to table1 by ParentID (1-to-many)
-----------------
code  class   ParentID
code1 class1  1
code2 class2  1
code3 class3  2
code4 class4  4

table3: data, joined to table2 by class and code (1-to-many)
-----------------
code  class   cost
code1 class1  1.00
code1 class1  10.00
code1 class1  26.00
code2 class2  5.00
code2 class2  0.00
code3 class3  1000.00

预期产出：

alias1 42.00
alias2 1000.00
alias4 0.00
alias3 0.00

Answer 1

var query = from x in Table1.AsEnumerable()
orderby x.Field<int>("Priority")
select new {
    Name = x.Field<string>("alias"),
    TotalCost = x.GetChildRows("Table1Table2")
            .Sum(c => c.GetChildRows("Table2Table3")
                    .Sum(tx => tx.Field<decimal>("cost")))
};

LINQ - 如何使用DataSet.DataRelation连接这些表并将一个字段相加？

1 个答案: