Question

我试图在ul / li中显示嵌套数据，但嵌套的子项未显示。看到我的代码，请告诉我那里有什么问题。

控制器：

public ActionResult Index()
{       
    List<MenuItem> allMenu = new List<MenuItem>
    {
        new MenuItem {Id=1,Name="Parent 1", ParentId=0},
        new MenuItem {Id=2,Name="child 1", ParentId=1},
        new MenuItem {Id=3,Name="child 2", ParentId=1},
        new MenuItem {Id=4,Name="child 3", ParentId=1},
        new MenuItem {Id=5,Name="Parent 2", ParentId=0},
        new MenuItem {Id=6,Name="child 4", ParentId=4}
    };

    List<MenuItem> mi = allMenu
    .Where(e => e.ParentId == 0) /* grab only the root parent nodes */
    .Select(e => new MenuItem
    {
        Id = e.Id,
        Name = e.Name,
        ParentId = e.ParentId,
        Children = allMenu.Where(x => x.ParentId == e.Id).ToList()
    }).ToList();

    ViewBag.menusList = mi;

    return View();
}

POCO课程：

public class MenuItem 
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int ParentId { get; set; }
    public virtual List<MenuItem> Children { get; set; }
}

查看：

@helper ShowTree(List<Scaffolding.Controllers.MenuItem> menusList)
{
    <ul>
        @foreach (var item in menusList)
        {
            <li>
                <span>@item.Name</span>
                @if (item.Children != null && item.Children.Any())
                {
                    @ShowTree(item.Children)
                }
            </li>
        }
    </ul>
}

@{
    var menuList = ViewBag.menusList as List<Scaffolding.Controllers.MenuItem>;
    @ShowTree(menuList);
}

如果您运行代码，那么您将看到子4未显示哪个是孩子3的孩子。请告知我需要更改我的代码。感谢

Answer 1

您的查询仅获取顶级元素（ParentId == 0），然后仅填充其直接子元素。

您的查询需要更改为填充所有级别的所有子元素。请注意，您的MeuItem不需要ParentId属性。

// Group the items by parentId and project to MenuItem
var groups = allMenu.ToLookup(x => x.ParentId, x => new MenuItem
{
    Id = x.Id,
    Name = x.Name,
});
// Assign the child menus to all items
foreach (var item in allMenu)
{
    item.children = groups[item.Id].ToList();
}
// Return just the top level items
ViewBag.menusList = groups[0].ToList();

作为旁注，请勿使用ViewBag。将模型传递给视图

return View(groups[0].ToList());

并在视图中

@model List<MenuItem>
....
@ShowTree(Model);

Answer 2

现在我可以解决我的问题。问题出在剃刀代码的逻辑上，我在这里评论这一行//.Where(e => e.ParentId == 0)我在这里添加工作代码。

@helper  ShowTree(List<NestedChild.Controllers.MenuItem> menu, int? parentid = 0, int level = 0)
{
    var items = menu.Where(m => m.ParentId == parentid);

    if (items.Any())
    {
        if (items.First().ParentId > 0)
        {
            level++;
        }

        <ul>
            @foreach (var item in items)
            {
            <li>
                @item.Name
            </li>
                @ShowTree(menu, item.Id, level);
            }
        </ul>
    }
}
@{
    var menuList = ViewBag.menusList as List<NestedChild.Controllers.MenuItem>;
    @ShowTree(menuList);
}

动作

public ActionResult Index()
{
    List<MenuItem> allMenu = new List<MenuItem>
    {
        new MenuItem {Id=1,Name="Parent 1", ParentId=0},
        new MenuItem {Id=2,Name="child 1", ParentId=1},
        new MenuItem {Id=3,Name="child 2", ParentId=1},
        new MenuItem {Id=4,Name="child 3", ParentId=1},
        new MenuItem {Id=5,Name="Parent 2", ParentId=0},
        new MenuItem {Id=6,Name="child 4", ParentId=4}
    };

    List<MenuItem> mi = allMenu
    //.Where(e => e.ParentId == 0) /* grab only the root parent nodes */
    .Select(e => new MenuItem
    {
        Id = e.Id,
        Name = e.Name,
        ParentId = e.ParentId,
        Children = allMenu.Where(x => x.ParentId == e.Id).ToList()
    }).ToList();

    ViewBag.menusList = mi;

    return View();
}

ASP.Net MVC：不显示嵌套子项的递归方法

2 个答案:

动作