递归函数中的 StackOverFlowException [英] StackOverFlowException inside a recursive function

问题描述

我在数据库中有一个表如下:

I have a table in database as follows:

MenuItem
-------------
MenuItemId    1 --------+
MenuItemName            |
ParentId      * --------+

现在我已经编写了一个递归函数来获取所有父菜单项及其子项.

Now I have written a recursive function to get all the Parent MenuItems with their children.

private ICollection<MenuItem> GetAllChildrenOfSpecificMenuItemRecursively(MenuItem menuItem, IEnumerable<MenuItem> menuItems)
{
    ICollection<MenuItem>  Children = null;
    foreach (MenuItem mi in menuItems)
    {
        if (mi.ParentMenuItemId != null)
        {
            if (mi.ParentMenuItemId == menuItem.MenuItemId)
            {
                Children.Add(mi);
            }
            else
            {
                return GetAllChildrenOfSpecificMenuItemRecursively(mi, menuItems);
            }
        }
    }

    return Children;
}

现在，我从另一个函数调用它，如下所示:

Now, I am calling it from another function as follows:

public IEnumerable<MenuItem> GetAllParentMenuItemsWithChildren()
{
    List<MenuItem> MenuItems = new List<MenuItem>();
    IEnumerable<MenuItem> AllMenuItems = null;

    using (MaxContext entityContext = new MaxContext())
    {
        AllMenuItems = (from e in entityContext.MenuItemSet select e).ToList();

        foreach (MenuItem menuItem in entityContext.MenuItemSet)
        {
            if (menuItem.ParentMenuItemId == null)
            {
                menuItem.Children = GetAllChildrenOfSpecificMenuItemRecursively(menuItem, AllMenuItems);
                MenuItems.Add(menuItem);
            }
        }
    }

    return MenuItems;
}

但它在递归函数中给了我stackoverflowException.我确信我在该功能上犯了一个小错误.有人能指出这个错误吗?

But it gives me stackoverflowException inside the recursive function. I am sure that I am making a minor mistake in that function. Can anybody point out that mistake?

推荐答案

我认为有一种更简单(也许更快)的方法可以在不使用递归的情况下做到这一点.像这样:

I think there is a simpler (and maybe faster) way of doing this without using recursion. Something like this:

    public ICollection<MenuItem> GetMenuItemsAsTreeList()
    {
        AllMenuItems = entityContext.MenuItemSet.ToList();

        Dictionary<int, MenuItem> dic = AllMenuItems.ToDictionary(n => n.Id, n => n);

        List<MenuItem> rootMenuItems = new List<MenuItem>();

        foreach (MenuItem menuItem in AllMenuItems)
        {
            if (menuItem.ParentMenuItemId.HasValue)
            {
                MenuItem parent = dic[menuItem.ParentMenuItemId.Value];
                menuItem.ParentMenuItem = parent;
                parent.SubMenuItems.Add(menuItem);
            }
            else
            {
                rootMenuItems.Add(menuItem);
            }
        }

        return rootMenuItems;
    }

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