TreeView使用泛型List動態加載數據源

來源：https://blogs.msmvps.com/deborahk/populating-a-treeview-control-from-a-list/

實體類

public class TreeViewItem
{
    public int ID { get; set; }
    public int ParentID { get; set; }
    public string Text { get; set; }
}

加載數據

List<TreeViewItem> treeViewList = new List<TreeViewItem>();

treeViewList.Add(new TreeViewItem() { 
          ParentID = 0, ID = 1, Text = "Parent node" });
treeViewList.Add(new TreeViewItem() { 
          ParentID = 1, ID = 2, Text = "First child node" });
treeViewList.Add(new TreeViewItem() { 
         ParentID = 1, ID = 3, Text = "Second child node" });
treeViewList.Add(new TreeViewItem() { 
         ParentID = 3, ID = 4, Text = "Child of second child node" });
treeViewList.Add(new TreeViewItem() { 
         ParentID = 3, ID = 5, Text = "Child of second child node" });

PopulateTreeView(0, null);

操作類：

private void PopulateTreeView(int parentId, TreeNode parentNode)
{
    var filteredItems = treeViewList.Where(item => 
                                item.ParentID == parentId);

    TreeNode childNode;
    foreach (var i in filteredItems.ToList())
    {
        if (parentNode == null)
            childNode = treeView1.Nodes.Add(i.Text);
        else
            childNode = parentNode.Nodes.Add(i.Text);

        PopulateTreeView(i.ID, childNode);
    }
}