從查詢動態生成TreeView控件（VB.NET）

Question

我以前從未使用過TreeViews，我希望顯示層次結構（n級的遞歸關系）。 數據（在數據集中可用 - 從數據庫查詢中檢索）具有以下結構：

__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

我正在嘗試生成以下輸出

- Patrick [1]
  - George [8]
    - Rodney [10]
  - Robert [9]

- Mark [2]
  - Scott [3]

- Julian [5]
  - John [6]

- Jason [4]

- Steve [7]

我正在嘗試生成Treeview控件但沒有使用Treeviews的經驗。 任何有關如何實現這一目標的反饋或示例都將非常感激。

Answer 1

要從DataTable填充TreeView，請嘗試以下代碼

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

VB.NET WindowsForms應用程序的代碼

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

ASP.NET應用程序的代碼

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

這里最重要的是一個通用且適應性強的算法，能夠執行所需的排序。 一旦到位，將值寫入TreeView很簡單，只需添加Nodes和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)

此代碼依賴於兩個數組（ NAME （字符串），其中還包括[原始位置]和PARENT （整數））並執行包含直到“第二級”，即主節點和第一個子節點。

我想你將有足夠的信息來理解如何處理TreeView並構建一個能夠執行你想要的排序的算法。