如何查找树视图子节点参考 [英] How to find Tree View Child Node Reference

问题描述

我正在VB中动态填充3级树状视图.我可以添加一个新的一级节点并设置一个对象变量，该变量允许我对其进行引用以更改值和其他属性，但是似乎无法对子节点执行相同的操作.这适用于第一级:
tvLevels.Nodes.Add(New TreeNode(strNodeName))
nodeLevel1 = tvLevels.FindNode(strNodeName)
nodeLevel1.Value = datareader("AALevelID")


但这不适用于子节点:
nodeLevel1.ChildNodes.Add(新的TreeNode(strNodeName))
nodeLevel2 = tvLevels.FindNode(strNodeName)
nodeLevel2.Value = datareader("AALevelID")
我收到错误消息
对象引用未设置为对象的实例"

这些对象声明为:
将nodeLevel1调暗为新的TreeNode
将nodeLevel2调暗为新的TreeNode

任何帮助将不胜感激.

I am dynamically populating a 3 level tree view in VB. I can add a new first level node and set a object variable that allows me to reference it to change the value and other properties, but I can''t seem to do the same with the child node. This works for the first level:
tvLevels.Nodes.Add(New TreeNode(strNodeName))
nodeLevel1 = tvLevels.FindNode(strNodeName)
nodeLevel1.Value = datareader("AALevelID")


but this doesn''t work for child nodes:
nodeLevel1.ChildNodes.Add(New TreeNode(strNodeName))
nodeLevel2 = tvLevels.FindNode(strNodeName)
nodeLevel2.Value = datareader("AALevelID")
I get the error
"Object reference not set to an instance of the object"

The objects are declared as:
Dim nodeLevel1 As New TreeNode
Dim nodeLevel2 As New TreeNode

Any help would be appreciated.

推荐答案

所有错误.当您编写New TreeNode(strNodeName)时，它已经返回了您的节点.您正在填充.所有对象都是您的，您怎么会想到使用FindNode的想法?为什么要搜索所有内容?

您的FindNode返回null，并且您正在尝试通过nodeLevel2.Value在下一行中取消引用该null，从而引发异常.

—SA

All wrong. When you write New TreeNode(strNodeName), it already returns you the node. You are populating. All object are yours, how could you come to the idea of using FindNode? Why searching for anything at all?

Your FindNode returns you null, and you are trying to de-reference the null in next line via nodeLevel2.Value which throws the exception.

—SA

不漂亮，但可以使用:



nodeLevel1.ChildNodes.Add(新的TreeNode(strNodeName))

对于tvLevels.Nodes中的每个nodeLevel1
对于nodeLevel1.ChildNodes中的每个nodeLevel2
如果nodeLevel2.Text = strNodeName然后
nodeLevel2.Value = datareader("AALevelID")
如果结束
下一个
下一个

Not pretty but it works:



nodeLevel1.ChildNodes.Add(New TreeNode(strNodeName))

For Each nodeLevel1 In tvLevels.Nodes
For Each nodeLevel2 In nodeLevel1.ChildNodes
If nodeLevel2.Text = strNodeName Then
nodeLevel2.Value = datareader("AALevelID")
End If
Next
Next

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