vb.net - LINQ to Objects - 祖 parent 、 parent 、子女关系

Question

我是 LINQ 的新手，我已经能够编写一些简单的语句。但是现在我有一个更复杂的情况，我无法弄清楚。

基本上，我正在尝试编写 LINQ to Objects 语句，其中关系是祖 parent 、 parent 、子女关系。 (您也可以将其称为主从关系。)

在 Legacy 代码中，这里是我试图完成的简化版本。

        Dim coverages As New List(Of Coverage)
        Dim coverage As Coverage 

        For Each rl In oClaimsPolicy.RiskLocations 

            coverage = New Coverage
            coverage.Level = "Location"

            'Get rl detail detail
            coverages.Add(coverage) 

            For Each ri In rl.RiskItems 

                coverage = New Coverage
                coverage.Level = "Item"

                'Get ri detail
                coverages.Add(coverage) 

                For Each rc In ri.RiskCoverages 

                    coverage = New Coverage
                    coverage.Level = "Coverage"

                    'Get rc detail here
                    coverages.Add(coverage) 

                Next 

            Next 

        Next

如果不清楚，一个Location可以有多个Items，一个Item可以有多个Coverages。我基本上想列出项目并显示祖 parent (Location)、 parent (Item) 和 child (Coverage) 之间的关系。

更新:

这是我想出的:

Dim coverages = oClaimsPolicy.RiskLocations. _
                  SelectMany(Function(rl) rl.RiskItems. _
                  SelectMany(Function(ri) ri.RiskCoverages. _
                  Select(Function(rc) New Coverage With {.Level = "Coverage"})))

然而，这只是列出了所有子项(Coverages)。

这是我正在寻找的结果:

Location
    Item 
       Coverage 
    Item 
       Coverage 
       Coverage 
Location 
    Item 
       Coverage 

因此，数据按位置和项目分组。

另一种查看方式是 ListView 或 Report。分组是按位置和项目完成的。

下面是一个例子

Location
    Item
        Coverage
    Item
        Coverage
        Coverage
Location
    Item
        Coverage

清楚了吗？

Answer 1

当我去测试它时，你的原始查询没有编译。这是一个版本:

Dim coverages = _
    From rl In oClaimsPolicy.RiskLocations _
    From ri in rl.RiskItems _
    From rc in ri.RiskCoverages _
    Select New Coverage With {.Level = "Coverage"}

现在，要获得您想要的结果，请尝试这样做:

dim create As Func(Of String, IEnumerable(Of Coverage)) = _
    Function (level) New Coverage() _
        { New Coverage With { .Level = level } }

Dim coverages = _
    From rl In oClaimsPolicy.RiskLocations _
    From cl In create("Location").Concat( _
            From ri In rl.RiskItems _
            From ci In create("  Item").Concat( _
                    From rc In ri.RiskCoverages _
                    From cc In create("    Coverage") _
                    Select cc) _
            Select ci) _
    Select cl

它是一堆嵌套的 SelectMany 和 Concat 表达式，它生成一个 Coverage 对象列表，如下所示:

Location
  Item
    Coverage
Location
  Item
    Coverage
  Item
    Coverage

这就是你想要的吗？