在遞歸函數中移除TreeView中的多個節點

Question

我有一個預建的TreeView控件。我想根據保存在數據庫中的值將這些節點作爲權限集移除。我使用遞歸方法刪除節點，但有些節點仍然存在，不會被刪除。這裏是我的代碼：

Private Sub setNodes() 
    For Each nd As TreeNode In TreeView1.Nodes 
     If nd.Name = "Students" AndAlso row.Item("CanAddStudents") = False AndAlso row.Item("CanViewStudents") = False AndAlso row.Item("CanImportStudents") = False Then 
      nd.Remove() 
      nd.Tag = False 
     End If 
     If Not nd.Tag = False Then 
      setNodes(nd) 
     End If 
     nd.Tag = True 
    Next 
End Sub 

Private Sub setNodes(ByVal nd As TreeNode) 
    For Each childNd As TreeNode In nd.Nodes 
     If childNd.Name = "Registration" AndAlso row.Item("CanAddStudents") = False Then 
      childNd.Remove() 
      childNd.Tag = False 
     ElseIf childNd.Name = "View_Registration" AndAlso row.Item("CanViewStudents") = False Then 
      childNd.Remove() 
      childNd.Tag = False 
     ElseIf childNd.Name = "Import_Student" AndAlso row.Item("CanImportStudents") = False Then 
      childNd.Remove() 
      childNd.Tag = False 
     End if 
    Next 
    If Not childNd.Tag = False Then 
     setNodes(childNd) 
    End If 
    childNd.Tag = True 
End Sub 

此代碼工作在單父節點及其子節點，但是當有超過1個父節點這是行不通的。如果有3個父節點，那麼其中一個父節點不會被刪除。

我改變了我的代碼如下。

Private Sub RemoveNodes(ByVal nc As TreeNodeCollection) 
    For i As Integer = nc.Count - 1 To 0 Step -1 
     If nc(i).Nodes.Count > 0 Then 
      RemoveNodes(nc(i).Nodes) 
     End If 
     If nc(i).Name = "Registration" AndAlso row.Item("CanAddStudents") = False Then 
      nc.RemoveAt(i) 
     ElseIf nc(i).Name = "View_Registration" AndAlso row.Item("CanViewStudents") = False Then 
      nc(i).Remove() 
     ElseIf nc(i).Name = "Import_Student" AndAlso row.Item("CanImportStudents") = False Then 
      nc(i).Remove() 
     ElseIf nc(i).Name = "Students" AndAlso row.Item("CanAddStudents") = False AndAlso row.Item("CanViewStudents") = False AndAlso row.Item("CanImportStudents") = False Then 
      nc(i).Remove() 
     End If 
    Next 
End Sub 

Answer 1

很難僅通過查看這些代碼的說法，但有一點，它看起來很奇怪，在我看來，在setNodes(TreeNode)方法，你只需要它自稱遞歸的最後一個子節點。如果您想要爲每個節點執行此操作，則需要將底部的If語句上移到您的For循環中。例如：

For Each childNd As TreeNode In nd.Nodes 
    If childNd.Name = "Registration" AndAlso row.Item("CanAddStudents") = False Then 
     childNd.Remove() 
     childNd.Tag = False 
    ElseIf childNd.Name = "View_Registration" AndAlso row.Item("CanViewStudents") = False Then 
     childNd.Remove() 
     childNd.Tag = False 
    ElseIf childNd.Name = "Import_Student" AndAlso row.Item("CanImportStudents") = False Then 
     childNd.Remove() 
     childNd.Tag = False 
    End if 

    'Put recursive call inside loop 
    If Not childNd.Tag = False Then 
     setNodes(childNd) 
    End If 
    childNd.Tag = True 
Next