如何使用“n”填充树视图？数据表的层次结构级别？ [英] How can I populate a treeview with "n" levels of hierarchy from a datatable?

问题描述

这段代码是硬编码的，可以将我的Tasks TreeView填充到三个级别。但是，我的任务列表在层次结构中可能有n级别，我想摆脱硬编码并提高灵活性。我的代码：

This block of code is hard-coded to populate my Tasks TreeView down to three levels. However, my list of Tasks could have "n" levels in the hierarchy and I want to get rid of the hard-coding and improve flexibility. My code:

TasksHierarchy.Nodes.Clear()
'populate treeview - add all top-level tasks
For Each dr As DataRow In DataSet1.DataTable1
   If dr.Item("ParentTaskID").Equals(DBNull.Value) Then 
   'task is at the top level
      TasksHierarchy.Nodes.Add("Task: " & dr.Item("TaskName") & "Task Type: " & dr.Item("TaskTypeName") & " - Owner: " & dr.Item("Name"))
   End If
Next
'add all second-level tasks
Dim child As Integer = 0
Dim grandchild As Integer = 0
For Each dr2 As DataRow In DataSet1.DataTable1
   For Each dr2Child As DataRow In BacklogView.DataSet1.DataTable1.Select("ParentTaskID='" & dr2.Item("JobTaskID") & "'")
      If child < TasksHierarchy.Nodes.Count - 1 Then
         TasksHierarchy.Nodes(child).Nodes.Add("Task: " & dr2Child.Item("TaskName") & " - Task Type: " & dr2Child.Item("TaskTypeName") & " - Owner: " & dr2Child.Item("Name"))
      End If
      'add all third-level tasks
      For Each dr2GrandChild As DataRow In DataSet1.DataTable1.Select("ParentTaskID='" & dr2Child.Item("JobTaskID") & "'")
                        TasksHierarchy.Nodes(child).Nodes(grandchild).Nodes.Add("Task: " & dr2GrandChild.Item("TaskName") & " - Task Type: " & dr2GrandChild.Item("TaskTypeName") & " - Owner: " & dr2GrandChild.Item("Name"))
      Next
      grandchild = grandchild + 1
   Next
   child = child + 1
Next

我尝试了什么：



我尝试制作分层DataGridView来显示依赖关系但是从在线示例的C＃转换为VB.Net不起作用，程序崩溃。

What I have tried:

I have tried making a hierarchical DataGridView to show the dependencies but converting from the online example's C# to VB.Net did not work and the program crashed.

推荐答案

遍历任意深层次的数据结构。

嗯....

这看起来像是一份工作： 递归



顶级处理基本相同，只是在 Add（） sa节点之后，它调用一个递归函数来处理直接的孩子。在该函数中，当一个节点 Add（） ed时，再次调用相同的函数来处理其子项等。

（这是Depth-first tree traversal。）



==========

这样的东西（我不是一个复杂的VB开发者.C＃是的。）：

Traversing an arbitrarily deep hierarchical data structure.
Hmmmm....
This looks like a job for: Recursion

The top level processing is essentially the same, except that after it Add()s a node, it calls a recursive function that deals with the direct children. In that function, when a node is Add()ed, the same function is called again to process its children, etc.
(This is a "Depth-first tree traversal".)

==========
Something like this (I'm not a sophisticated VB dev. C# yes.):

' At the appropriate place in the code...
Private Sub AddDescendents(ByVal nodes As TreeNodeCollection, ByVal data As DataTable, ByVal taskID as String)
  For Each dr As DataRow in data.Select("ParentTaskID='" & taskID & "'")
    Dim newNode As TreeNode
    newNode = nodes.Add("Task: " & dr.Item("TaskName") & _
                        " - Task Type: " & dr.Item("TaskTypeName") & _
                        " - Owner: " & dr.Item("Name"))
    AddDescendents(newNode.Nodes, data, dr.Item("JobTaskID"))
  Next
End Sub

' elsewhere ...
TasksHierarchy.BeginUpdate()
TasksHierarchy.Nodes.Clear()
Dim nodes As TreeNodeCollection = TasksHierarchy.Nodes
'populate treeview - add all top-level tasks
For Each dr As DataRow In DataSet1.DataTable1
  If IsDBNull(dr.Item("ParentTaskID")) Then 
    'task is at the top level
    Dim newNode As TreeNode
    newNode = nodes.Add("Task: " & dr.Item("TaskName") & _
                        " - Task Type: " & dr.Item("TaskTypeName") & _
                        " - Owner: " & dr.Item("Name"))
    AddDescendents(newNode.Nodes, DataSet1.DataTable1, dr.Item("JobTaskID"))
  End If
Next
TasksHierarchy.EndUpdate()

（如果我更了解VB，可以合并一些复制......）

(Some of the duplication could be consolidated if I knew VB better...)

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