C#中如何遍历TreeView的所有跟节点

foreach(TreeNode node in TreeView.Nodes)
{
}

SelectByID(this.TreeView1,this.TextBox1.Text.ToString());
private void SelectByID(TreeView tv,string ID)
{
foreach(TreeNode tn in tv.Nodes)
{
if(rec(tv,tn,ID))
{
break;
}
}
}
private bool rec(TreeView tv,TreeNode tn,string ID)
{
string ss=tn.Text;
if(tn.ID==ID)
{
tv.SelectedNodeIndex=tn.GetNodeIndex();
return true;
}
else
{
bool t=false;
foreach(TreeNode ctn in tn.Nodes)
{
if(rec(tv,ctn,ID))
{
t=true;
break;
}
}
return t;
}
}
或者（遍历选中节点）
private void GetTreeSelected(TreeNodeCollection trees)
{
foreach(TreeNode tn in trees)