Generate TreeView Control Dynamically from Query (VB.NET) - asp.net

Question

I have never used TreeViews in the past and I want to display a hierarchical structure (recursive relationship of n levels). The data (available in a dataset - retrieved from database query) is in the following structure:
__ID__ | __NAME__ | __PARENT__
1 | Patrick |
2 | Mark |
3 | Scott | 2
4 | Jason |
5 | Julian |
6 | John | 6
7 | Steve |
8 | George | 1
9 | Robert | 1
10 | Rodney | 8
I'm trying to produce the following output
- Patrick [1]
- George [8]
- Rodney [10]
- Robert [9]
- Mark [2]
- Scott [3]
- Julian [5]
- John [6]
- Jason [4]
- Steve [7]
I'm trying to generate the Treeview control but have no experience with Treeviews. Any feedback or examples on how to achieve this would be really appreciated.

Answer 1

To fill the TreeView from a DataTable, try the following code
Dim DataTable1 As New DataTable
Private Sub FillTestTable()
DataTable1.Columns.Add("ID", GetType(Integer))
DataTable1.Columns.Add("NAME", GetType(String))
DataTable1.Columns.Add("PARENT", GetType(Integer))
DataTable1.Columns.Add("LEVEL", GetType(Integer))
DataTable1.Rows.Add(1, "Patrick")
DataTable1.Rows.Add(2, "Mark")
DataTable1.Rows.Add(3, "Scott", 2)
DataTable1.Rows.Add(4, "Jason")
DataTable1.Rows.Add(5, "Julian")
DataTable1.Rows.Add(6, "John", 5)
DataTable1.Rows.Add(7, "Steve")
DataTable1.Rows.Add(8, "George", 1)
DataTable1.Rows.Add(9, "Robert", 1)
DataTable1.Rows.Add(10, "Rodney", 8)
Dim i As Integer
For i = 0 To DataTable1.Rows.Count - 1
Dim ID1 As String = DataTable1.Rows(i).Item("ID").ToString
DataTable1.Rows(i).Item("LEVEL") = FindLevel(ID1, 0)
Next
End Sub
Private Function FindLevel(ByVal ID As String, ByRef Level As Integer) As Integer
Dim i As Integer
For i = 0 To DataTable1.Rows.Count - 1
Dim ID1 As String = DataTable1.Rows(i).Item("ID").ToString
Dim Parent1 As String = DataTable1.Rows(i).Item("PARENT").ToString
If ID = ID1 Then
If Parent1 = "" Then
Return Level
Else
Level += 1
FindLevel(Parent1, Level)
End If
End If
Next
Return Level
End Function
Code for VB.NET WindowsForms application
Private Sub CreateTree()
Dim MaxLevel1 As Integer = CInt(DataTable1.Compute("MAX(LEVEL)", ""))
Dim i, j As Integer
For i = 0 To MaxLevel1
Dim Rows1() As DataRow = DataTable1.Select("LEVEL = " & i)
For j = 0 To Rows1.Count - 1
Dim ID1 As String = Rows1(j).Item("ID").ToString
Dim Name1 As String = Rows1(j).Item("NAME").ToString
Dim Parent1 As String = Rows1(j).Item("PARENT").ToString
If Parent1 = "" Then
TreeView1.Nodes.Add(ID1, Name1)
Else
Dim TreeNodes1() As TreeNode = TreeView1.Nodes.Find(Parent1, True)
If TreeNodes1.Length > 0 Then
TreeNodes1(0).Nodes.Add(ID1, Name1)
End If
End If
Next
Next
End Sub
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
FillTestTable()
CreateTree()
TreeView1.ExpandAll()
End Sub
Code for ASP.NET application
Private Sub CreateTree()
Dim MaxLevel1 As Integer = CInt(DataTable1.Compute("MAX(LEVEL)", ""))
Dim i, j As Integer
For i = 0 To MaxLevel1
Dim Rows1() As DataRow = DataTable1.Select("LEVEL = " & i)
For j = 0 To Rows1.Count - 1
Dim ID1 As String = Rows1(j).Item("ID").ToString
Dim Name1 As String = Rows1(j).Item("NAME").ToString
Dim Parent1 As String = Rows1(j).Item("PARENT").ToString
If Parent1 = "" Then
TreeView1.Nodes.Add(New TreeNode(Name1, ID1))
Else
Dim Node1 As TreeNode = GetChildByValue(Parent1, TreeView1.Nodes)
If Not Node1 Is Nothing Then
Node1.ChildNodes.Add(New TreeNode(Name1, ID1))
End If
End If
Next
Next
End Sub
Private Function GetChildByValue(ByVal ID1 As String, ByVal NodeCollection1 As TreeNodeCollection) As TreeNode
For Each TreeNode1 As TreeNode In NodeCollection1
If TreeNode1.Value = ID1 Then
Return TreeNode1
Else
Dim TreeNode2 As TreeNode = GetChildByValue(ID1, TreeNode1.ChildNodes)
If Not TreeNode2 Is Nothing Then
Return TreeNode2
End If
End If
Next
Return Nothing
End Function
Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
FillTestTable()
CreateTree()
TreeView1.ExpandAll()
End Sub

Answer 2

The big deal here is coming with a generic and adaptable enough algorithm capable of performing the required sorting. Once this is in place, writing the values into the TreeView is straightforward, just adding Nodes and ChildNodes.
Dim NAME(10) As String
Dim PARENT(10) As Integer
Dim curID As Integer = 0
curID = 1
NAME(curID) = "Patrick [" & curID.ToString() & "]"
PARENT(curID) = 0
curID = curID + 1
NAME(curID) = "Mark [" & curID.ToString() & "]"
PARENT(curID) = 0
curID = curID + 1
NAME(curID) = "Scott [" & curID.ToString() & "]"
PARENT(curID) = 2
curID = curID + 1
NAME(curID) = "Jason [" & curID.ToString() & "]"
PARENT(curID) = 0
curID = curID + 1
NAME(curID) = "Julian [" & curID.ToString() & "]"
PARENT(curID) = 0
curID = curID + 1
NAME(curID) = "John [" & curID.ToString() & "]"
PARENT(curID) = 6
curID = curID + 1
NAME(curID) = "Steve [" & curID.ToString() & "]"
PARENT(curID) = 0
curID = curID + 1
NAME(curID) = "George [" & curID.ToString() & "]"
PARENT(curID) = 1
curID = curID + 1
NAME(curID) = "Robert [" & curID.ToString() & "]"
PARENT(curID) = 1
curID = curID + 1
NAME(curID) = "Rodney [" & curID.ToString() & "]"
PARENT(curID) = 8
Dim completed As Boolean = False
Dim firstIteration As Boolean = True
Dim totIDs As Integer = 10
Do
curID = 0
Do
curID = curID + 1
If (firstIteration) Then
If (PARENT(curID) = 0 And TreeView1.FindNode(NAME(curID)) Is Nothing) Then
TreeView1.Nodes.Add(New TreeNode(NAME(curID)))
End If
Else
If (PARENT(curID) > 0) Then
Dim targetNodes As TreeNodeCollection = TreeView1.Nodes
Dim count As Integer = 0
If (TreeView1.FindNode(NAME(curID)) Is Nothing) Then
For Each node As TreeNode In targetNodes
count = count + 1
If (node.Text.Contains("[" & PARENT(curID).ToString() & "]")) Then
node.ChildNodes.Add(New TreeNode(NAME(curID)))
Exit For
End If
Next
End If
End If
End If
Loop While (curID < totIDs)
If (firstIteration) Then
firstIteration = False
Else
Exit Do 'Just two iterations
End If
Loop While (Not completed)
This code relies on two arrays (NAME (strings), which also includes [original position] and PARENT (integers)) and performs the inclusions until the "second level", that is, main nodes and first child nodes.
I guess that you will have enough information to understand how to deal with TreeView and to build an algorithm capable of performing the sorting you want.