LINQ查询以获取无尽的子元素 [英] LINQ Query to get endless child elements

问题描述

Assume that I have a Super Parent - "Super Parent"
Under Super Parent , I have Grand Parent1, Grand Parent2 , Grad Parent3 , This list can be increased by the user
Under Grand Parents , there may be parents , like Parent 1 , Parent 2 , Parent3 etc...this list can also increase 
Now Parent1 may have direct kids as File 1, File 2, File 3
But Parent 2 may have more child categories like Sub Parent1, Sub Parent 2 etc ...
So the whole point is , The list can increase horizonatally and vertically without limits at any time
I
am trying to write a LINQ Query that gets alll category names under
Super Parent, Just the Category names not the last File 1 and File 2
etc names, I wrote a query for 2 levels, can some one help me in
getting a generic query out so taht will accomodate any changes to the
tree and my requirement

public Dictionary<int, string> GetMenuCategory()
        {
            SampleDB db = new SampleDB();
            Dictionary<int, string> returnDict = new Dictionary<int, string>();
 
 
            var query = from q in db.OptionsMenu
                        where q.ParentMenuID == 3
                        select q;
            
 
            foreach (var a in query)
            {
                returnDict.Add(a.MenuID, a.MenuName);
                var query2 = from j in db.OptionsMenu
                             where j.ParentMenuID == a.MenuID
                             select j;
                foreach (var b in query2)
                {
                    returnDict.Add(b.MenuID, b.MenuName);
 
                }
 
                
            }
 
            return returnDict;
           
        }

---

---

ctrlnick

推荐答案

您必须编写一个递归函数:

public 静态 KeyValuePair < int ， string >> GetMenuCategory( int parentId)

You'd have to write a recursive function:

public static IEnumerable<KeyValuePair<int, string>> GetMenuCategory(int parentId)

{

var x = 来自，q 位于 db.OptionsMenu

    var x = from q in db.OptionsMenu

其中 q.ParentID == parentId

            where q.ParentID == parentId

选择 新 KeyValuePair < int ， 字符串>(q.MenuID，q.MenuName);

            select new KeyValuePair<int, string>(q.MenuID, q.MenuName);

返回 x.SelectMany(k => GetMenuCategory(k.Key)).Concat(x);

    return x.SelectMany(k => GetMenuCategory(k.Key)).Concat(x);

}

然后您可以通过执行类似"GetMenuCategory(3)"的操作来调用它.

我还建议您使用除Dictionary< int，string>以外的其他容器，因为在Linq上下文中很难使用.

您可以自己获取所有项目的IEnumerable，然后执行所需的任何操作:

}

Then you could call it by doing something like "GetMenuCategory(3)".

I would also advise you to use another container other than Dictionary<int, string>, as it's hard to work with when you're in a Linq context.

You could just fetch an IEnumerable of all the items themselves, then do whatever you want after that:

public 静态 商品> GetMenuCategory( int parentId)

public static IEnumerable<Item> GetMenuCategory(int parentId)

{

var x = 来自，q 位于 db.OptionsMenu

    var x = from q in db.OptionsMenu

其中 q.ParentID == parentId

            where q.ParentID == parentId

选择 q;

            select q;

返回 x.SelectMany(k => GetMenuCategory(k.ParentID)).Concat(x);

    return x.SelectMany(k => GetMenuCategory(k.ParentID)).Concat(x);

}

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