LINQ到基于分组填充树状 [英] LINQ to populate treeview based upon grouping

问题描述

我发现这个SO C＃的答案，但似乎无法得到这个工作：
的 C＃填充树视图从LINQ对象

I found this C# answer on S.O., but can't seem to get this working: c# populate treeview from LINQ object

在我的情况下，假设我有一个名单（共Report_Data ）其中，例如，看起来是这样的：

In my case, suppose I have a List(Of Report_Data) which, for example, looks like this:

Var1   Var2        
V1     Sub Item 1      
V1     Sub Item 2      
V1     Sub Item 3      
V2     Sub Item 1      
V2     Sub Item 2     
V3     Sub Item 1

和我期待使用LINQ来填充一个TreeView的样子：

And I'm looking to use LINQ to fill a treeview to look like:

V1 (CheckBox)
-------Sub Item 1  (CheckBox)
-------Sub Item 2  (CheckBox)
-------Sub Item 3  (CheckBox)
V2 (CheckBox)
-------Sub Item 1  (CheckBox)
-------Sub Item 2  (CheckBox)
V3 (CheckBox)
-------Sub Item 1  (CheckBox)

---

所以，在我的树视图填充程序中，我创建了以下内存查询：

---

So, in my Treeview-filling routine, I create the following in-memory query:

    Dim GroupedReports = From Rpt As Report_Data In ReportsToBeProcessed
                         Group Rpt By Rpt.Var1 Into Group

然后，我以为我可以通过组和循环再组合的对象来填充树视图 - 线沿线的东西：

And then I thought I could loop through the Groups and then the grouped objects to fill the treeview - something along the lines of:

    For Each Grp As Object In GroupedReports 
        ... Add Parent node ...
        For Each Rpt As Report_Data In Grp
            ... Add Child Node ...
        Next
    Next

首先，我不知道如何使用的数据类型为我的 GRP 变量，其次它似乎并不奏效......结果
我如何正确地做到这一点？

Firstly, I don't know what data-type to use for my Grp variable and secondly it doesn't seem to be working...
How do I do this correctly?

推荐答案

像这样的东西，你的意思是？

Something like this, you mean?

（对不起，从来不写VB了，所以最好我能做的就是C＃）

(sorry, never write VB anymore, so best I can do is C#)

var grped = 
    from report in reports
    group report by report.Var1 into grp
    select grp;
var treeView = new System.Windows.Forms.TreeView();
foreach(var grouping in grped)
{
    var nodeFor = treeView.Nodes.Add(grouping.Key);
    foreach(var item in grouping)
    {
        var subitem = nodeFor.Nodes.Add(item.Var2);
    }
}

编辑：
中的按组构建返回一组 IGrouping< TKEY的，TValue> - 你可以种认为这是一个键值对，关键是你通过分组的事情，该值是匹配该密钥的所有元素

The "group by" construct returns a set of IGrouping<TKey, TValue> - you can kind of think of this as a key-value pair, with the key being the thing you grouped by, and the value being all elements that matched that key.

下面是VB.Net代码，我相信：

Here is the VB.Net code I believe:

Dim grped = From report In reports
            Group report By report.Var1 into grp
            Select grp

Dim treeView as New System.Windows.Forms.TreeView()

For Each grouping In grped
    Dim nodeFor = treeView.Nodes.Add(grouping.Key)
    For Each item In grouping
        Dim subitem = nodeFor.Nodes.Add(item.Var2)
    Next
Next

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