如何：循环访问 Windows 窗体 TreeView 控件的所有节点
若要对节点值执行一些计算，检查 Windows 窗体 TreeView 控件中的每个节点有时很有用。 可使用递归方法（VB.NET 中的递归过程）来完成此操作，该方法循环访问树的每个集合中的每个节点。
树视图中的每个 TreeNode 对象都具有可用于导航树视图的属性：FirstNode、LastNode、NextNode、PrevNode 和 Parent。 Parent 属性的值是当前节点的父节点。 如果存在当前节点的子节点，则会在其 Nodes 属性中列出。 TreeView 控件本身具有 TopNode 属性，该属性是整个树视图的根节点。
递归方法
递归方法使用处理树节点的方法，然后为每个子节点调用相同的方法。 重复此过程，直到树中的所有节点均被处理。 此方法的缺点是，如果树很大，可能会遇到堆栈溢出错误并且内存不足。
以下示例显示如何输出每个 TreeNode 对象的 Text 属性：
private void PrintRecursive(TreeNode treeNode)
{
// Print the node.
System.Diagnostics.Debug.WriteLine(treeNode.Text);
MessageBox.Show(treeNode.Text);
// Visit each node recursively.
foreach (TreeNode tn in treeNode.Nodes)
{
PrintRecursive(tn);
}
}
// Call the procedure using the TreeView.
private void CallRecursive(TreeView treeView)
{
// Print each node recursively.
foreach (TreeNode n in treeView.Nodes)
{
//recursiveTotalNodes++;
PrintRecursive(n);
}
}
Private Sub PrintRecursive(n As TreeNode)
System.Diagnostics.Debug.WriteLine(n.Text)
MessageBox.Show(n.Text)
Dim aNode As TreeNode
For Each aNode In n.Nodes
PrintRecursive(aNode)
Next
End Sub
' Call the procedure using the top nodes of the treeview.
Private Sub CallRecursive(aTreeView As TreeView)
Dim n As TreeNode
For Each n In aTreeView.Nodes
PrintRecursive(n)
Next
End Sub
private:
void PrintRecursive(TreeNode^ treeNode)
{
// Print the node.
System::Diagnostics::Debug::WriteLine(treeNode->Text);
MessageBox::Show(treeNode->Text);
// Print each node recursively.
System::Collections::IEnumerator^ myNodes = (safe_cast<System::Collections::IEnumerable^>(treeNode->Nodes))->GetEnumerator();
try
{
while (myNodes->MoveNext())
{
TreeNode^ tn = safe_cast<TreeNode^>(myNodes->Current);
PrintRecursive(tn);
}
}
finally
{
delete(myNodes);
}
}
// Call the procedure using the TreeView.
void CallRecursive(TreeView^ treeView)
{
// Print each node recursively.
TreeNodeCollection^ nodes = treeView->Nodes;
System::Collections::IEnumerator^ myNodes = (safe_cast<System::Collections::IEnumerable^>(nodes))->GetEnumerator();
try
{
while (myNodes->MoveNext())
{
TreeNode^ n = safe_cast<TreeNode^>(myNodes->Current);
PrintRecursive(n);
}
}
finally
{
delete(myNodes);
}
}
非递归方法
以下示例是使用 Queue<T> 集合遍历树节点的替代迭代方法。 此方法不遵循节点的父子关系，仅确保输出每个节点。 如果要处理每个树节点及其子节点，首先使用 Stack<T> 集合
private void PrintNonRecursive(TreeNode treeNode)
{
if (treeNode != null)
{
//Using a queue to store and process each node in the TreeView
Queue<TreeNode> staging = new Queue<TreeNode>();
staging.Enqueue(treeNode);
while (staging.Count > 0)
{
treeNode = staging.Dequeue();
// Print the node.
System.Diagnostics.Debug.WriteLine(treeNode.Text);
MessageBox.Show(treeNode.Text);
foreach (TreeNode node in treeNode.Nodes)
{
staging.Enqueue(node);
}
}
}
}
// Call the procedure using the TreeView.
private void CallNonRecursive(TreeView treeView)
{
// Print each node.
foreach (TreeNode n in treeView.Nodes)
{
PrintNonRecursive(n);
}
}
Private Sub PrintNonrecursive(n As TreeNode)
If n IsNot Nothing Then
Dim staging As Queue(Of TreeNode) = New Queue(Of TreeNode)
staging.Enqueue(n)
While staging.Count > 0
n = staging.Dequeue()
'Print the node.
System.Diagnostics.Debug.WriteLine(n.Text)
MessageBox.Show(n.Text)
Dim node As TreeNode
For Each node In n.Nodes
staging.Enqueue(node)
Next
End While
End If
End Sub
Private Sub CallNonRecursive(aTreeView As TreeView)
Dim n As TreeNode
For Each n In aTreeView.Nodes
PrintNonrecursive(n)
Next
End Sub
private:
void PrintNonRecursive(TreeNode^ treeNode)
{
//Using a queue to store and process each node in the TreeView
Queue^ staging = gcnew Queue();
staging->Enqueue(treeNode);
while (staging->Count > 0)
{
treeNode = safe_cast<TreeNode^>(staging->Dequeue());
// Print the node.
System::Diagnostics::Debug::WriteLine(treeNode->Text);
MessageBox::Show(treeNode->Text);
System::Collections::IEnumerator^ children = (safe_cast<System::Collections::IEnumerable^>(treeNode->Nodes))->GetEnumerator();
try
{
while (children->MoveNext())
{
staging->Enqueue(children->Current);
}
}
finally
{
delete(children);
}
}
// Print the node.
System::Diagnostics::Debug::WriteLine(treeNode->Text);
MessageBox::Show(treeNode->Text);
// Print each node recursively.
System::Collections::IEnumerator^ myNodes = (safe_cast<System::Collections::IEnumerable^>(treeNode->Nodes))->GetEnumerator();
try
{
while (myNodes->MoveNext())
{
TreeNode^ tn = safe_cast<TreeNode^>(myNodes->Current);
PrintRecursive(tn);
}
}
finally
{
delete(myNodes);
}
}
// Call the procedure using the TreeView.
void CallNonRecursive(TreeView^ treeView)
{
// Print each node recursively.
TreeNodeCollection^ nodes = treeView->Nodes;
System::Collections::IEnumerator^ myNodes = (safe_cast<System::Collections::IEnumerable^>(nodes))->GetEnumerator();
try
{
while (myNodes->MoveNext())
{
TreeNode^ n = safe_cast<TreeNode^>(myNodes->Current);
PrintNonRecursive(n);
}
}
finally
{
delete(myNodes);
}
}
