c# - 在 C# 中刷新 TreeView 后展开选定的节点

Question

我有一个包含很多项目的 TreeView

当我展开一个项目及其子项并调用刷新方法后，展开的项目子项会折叠起来。

你能告诉我如何存储所选节点并在刷新后再次调用 Expand 方法吗...

我试过了:

 TreeNode selectedNode = new TreeNode();
 TreeNode selectedNode = SelectedTreeNode();  //method which takes selected node from TV
 RestoreFolderTreeWithLastSelectedItem(); //method which initialise treeview object
 //here I want to call Expand() method but it not exists to TreeNode.

对于 TreeView ，我使用了 Windows.Controls.treeView 命名空间 我是初学者... 谢谢

我用图片给你解释

我展开了所有项目:

如果我按 F5 或调用刷新函数 (RestoreFolderTreeWithLastSelectedItem();)，它们将像这样折叠:

而不是第一张图片...

Answer 1

我将它与 WinForms TreeView 一起使用。它在刷新之间保存节点展开状态:

// Save the path of the expanded tree branches
var savedExpansionState = treeView1.Nodes.GetExpansionState();

treeView1.BeginUpdate();

// TreeView is populated
// ...

// Once it is populated, we need to restore expanded nodes
treeView1.Nodes.SetExpansionState(savedExpansionState);

treeView1.EndUpdate();

实现代码如下:

public static class TreeViewExtensions
{
    public static List<string> GetExpansionState(this TreeNodeCollection nodes)
    {
        return nodes.Descendants()
                    .Where(n => n.IsExpanded)
                    .Select(n => n.FullPath)
                    .ToList();
    }

    public static void SetExpansionState(this TreeNodeCollection nodes, List<string> savedExpansionState)
    {
        foreach (var node in nodes.Descendants()
                                  .Where(n => savedExpansionState.Contains(n.FullPath)))
        {
            node.Expand();
        }
    }

    public static IEnumerable<TreeNode> Descendants(this TreeNodeCollection c)
    {
        foreach (var node in c.OfType<TreeNode>())
        {
            yield return node;

            foreach (var child in node.Nodes.Descendants())
            {
                yield return child;
            }
        }
    }
}