Question

我真的很喜欢编码我有一个用计时器刷新的树视图。如何确保每次刷新时都会突出显示所选节点

感谢任何帮助感谢

以下是我的代码：

    private void PopulateTree(ListObjectsResponse buckets)
    {
        treeView1.Nodes.Clear();
        List<TreeItem> items = new List<TreeItem>();
        foreach (S3Object obj in buckets.S3Objects)
        {
            treeView1.Nodes.Add(new TreeNode(obj.Key));
        }
    }

    private void button4_Click_1(object sender, EventArgs e)
    {
        timer1.Enabled = true;
        existingBucketName = label3.Text + "-DP";
        AmazonS3Client client = new AmazonS3Client();
        ListObjectsRequest listRequest = new ListObjectsRequest
        {
            BucketName = existingBucketName,
        };

        try
        {
            ListObjectsResponse listResponse;
            listResponse = client.ListObjects(listRequest);
            PopulateTree(listResponse);
        }
        catch
        {
            timer1.Enabled = false;
            MessageBox.Show("There is no folder for this user");
        }
    }

Answer 1

假设o.Key是一个字符串，并且每个字符串都是唯一的并且在buckets.S3Objects中最多出现一次，请尝试在重新填充TreeView之前保存所选值，然后再次选择它之后。

private void PopulateTree(ListObjectsResponse buckets)
{
    // Since you're about to clear out all current TreeNode instances, storing a
    // reference to SelectedNode is not enough. You're setting o.Key as the Text
    // for each TreeNode, so save the selected node's Text value. 
    var selectedText
        = treeView1.SelectedNode == null ? "" : treeView1.SelectedNode.Text;

    // Repopulate your TreeView with new TreeNodes
    treeView1.Nodes.Clear();
    treeView1.Nodes.AddRange(buckets.S3Objects.Select(o => new TreeNode(o.Key)).ToArray())

    // Look for the TreeNode with the same Text that you had selected before.
    // If it's not found, then SelectedNode will be set to null
    treeView1.SelectedNode =
        = treeView1.Nodes.Cast<TreeNode>()
                         .SingleOrDefault(n => n.Text == selectedText);
}

上述几种方法，例如Select，Cast和SingleOrDefault，都是LINQ的一部分。

Answer 2

假设这是您正在讨论的ASP.NET（不是ASP.NET MVC），您可以在Page_Load()事件处理程序中执行此操作。请务必检查IsPostBack == true

例如，

private void Page_Load(object sender, EventArgs e)
{
  if (!IsPostBack)
  {
    // set selected node here
  }
}

如果您使用的是ASP.NET MVC，则只需将该属性存储在ViewBag中。

在C＃中，如何在刷新时选择Treeview节点

2 个答案: