asp.net - 树视图选择的节点总是返回 null

Question

我使用下面的代码将新类别添加到我的数据库中的类别表中，但 selectedNode 的返回值始终为空。问题是什么？

protected void btnAddNode_Click(object sender, EventArgs e)
{
    string selectedNodeValue = CategoryTreeView.SelectedNode.Value;
     using (mydbEntities context = new mydbEntities())
        {
            int id = Int32.Parse(selectedNodeValue);
            Category obj = new Category();
            obj.Name = "bla bla";
            obj.CategoryParentId_FK = id;
            context.Categories.AddObject(obj);
            context.SaveChanges();
        }

    bindTreeView();
}

还有一件事，我的 categorytreeview 在更新面板中

这是我的标记

<div id="MyTreeDiv" class="TreeContiner">
                <asp:TreeView ID="CategoryTreeView" runat="server" ShowLines="true" 
                    LineImagesFolder="images/treeRTLlines" CssClass="AspNet-TreeView" 
                    onselectednodechanged="CategoryTreeView_SelectedNodeChanged">
                <NodeStyle CssClass="AspNet-TreeView-Nodes" />
                <SelectedNodeStyle  CssClass="AspNet-TreeView-Selected-Nodes" />
                </asp:TreeView>
                <div class="treeTools">

                <asp:LinkButton ID="btnAddNode" runat="server" CausesValidation="False" 
                                            CssClass="treeToolsLnk"
                                            Text="" onclick="btnAddNode_Click"><img src="Images/refresh.png" /></asp:LinkButton>

这是我的 bindtreeview 方法

#region bindTreeView
private void bindTreeView()
{


    CategoryTreeView.Nodes.Clear();
    using (mydbEntities context = new mydbEntities())
    {


        var parents = context.Categories.Where(a => a.CategoryParentId_FK == null).OrderBy(a => a.Name);

        if (parents.Any())
        {
            foreach (var p in parents)
            {
                TreeNode root = new TreeNode(p.Name, p.Id.ToString());
                root.SelectAction = TreeNodeSelectAction.Select;
                CreateNode(root);
                CategoryTreeView.Nodes.Add(root);
            }
        }



    }


}
void CreateNode(TreeNode node)
{
    using (mydbEntities context = new mydbEntities())
    {
        int p = Int32.Parse(node.Value.ToString());
        var childrens = context.Categories.Where(a => a.CategoryParentId_FK == p).OrderBy(a => a.Name);
        if (childrens.Any())
        {
            foreach (var c in childrens)
            {
                TreeNode tnode = new TreeNode(c.Name, c.Id.ToString());
                tnode.SelectAction = TreeNodeSelectAction.Select;
                node.ChildNodes.Add(tnode);
                CreateNode(tnode);

            }
        }

    }


}

#endregion

Answer 1

似乎您想获取所选节点的值。这样做的方法是使用SelectedNodeChanged。

<asp:TreeView id="CategoryTreeView"
            Font-Names= "Arial"
            ForeColor="Blue"
            SelectedNodeStyle-ForeColor="Green"
            SelectedNodeStyle-VerticalPadding="0"
            OnSelectedNodeChanged="Select_Change"   
            runat="server">

CS：

void Select_Change(Object sender, EventArgs e)
{

     string selectedNodeValue = CategoryTreeView.SelectedNode.Value;
     using (mydbEntities context = new mydbEntities())
        {
            int id = Int32.Parse(selectedNodeValue);
            Category obj = new Category();
            obj.Name = "bla bla";
            obj.CategoryParentId_FK = id;
            context.Categories.AddObject(obj);
            context.SaveChanges();
        }

    bindTreeView();

}