how to get sub data in entityframework core?

Question

how to get sub data in entityframework core?

mc 5,186

I have table:

Id	ParentId
1
2	1
3	1
4	2
5	2
6	3
7	10
8	11
9
10
11

public class Comp{ [Key] public string Id{get;set;} public string TopId{get;set;} }

I want to get all Ids that related to the one Id.

If Id=1 I want to get 2,3,4,5,6

If Id= 2 I want to get 4,5

If Id=6 I want to get 6

how to do this in ef core?

Jack J Jun 24,881 Reputation points Microsoft External Staff

2023-02-21T09:27:25.23+00:00

@打玻璃， Welcome to Microsoft Q&A, I am not clear about your meaning about get all Ids that related to the one Id.

Could you describe your example in more detail? I can understand If Id= 2 I want to get 4,5. But I am confused about your Id=1 and Id=6.
mc 5,186 Reputation points

2023-02-21T09:54:44.23+00:00

Id = 1 then I get the sub data of Id = 2 and Id = 3 because it's parentId=1 and then Id=4,Id=5(parentId=2),Id=6(parentId=3)

If Id= 6 there is no data that parentId=6 so only 6 will be return.

to find the sub data and its selft.
Jack J Jun 24,881 Reputation points Microsoft External Staff

2023-02-22T02:31:58.3133333+00:00
@打玻璃, thanks for the feedback, based on your description, we have to use recursion to do it. Also according to my test, PatriceSc's Answer is good.

However, I added the following code to consider that If Id= 6 there is no data that parentId=6 so only 6 will be return.

foreach(var testId in new string[]{"1","2","6"}) { var result=GetChildsFor(testId); if(result.Count()==0) ->added { Console.WriteLine(testId + ": " + testId); } else { Console.WriteLine(testId + ": " + string.Join(", ", result.OrderBy(o=>o))); } }
Jack J Jun 24,881 Reputation points Microsoft External Staff

2023-03-02T07:22:44.73+00:00

@打玻璃, is any update for this question?

1 answer

Your answer

Jack J Jun 24,881 Reputation points Microsoft External Staff

2023-02-21T09:27:25.23+00:00

@打玻璃， Welcome to Microsoft Q&A, I am not clear about your meaning about get all Ids that related to the one Id.

Could you describe your example in more detail? I can understand If Id= 2 I want to get 4,5. But I am confused about your Id=1 and Id=6.
mc 5,186 Reputation points

2023-02-21T09:54:44.23+00:00

Id = 1 then I get the sub data of Id = 2 and Id = 3 because it's parentId=1 and then Id=4,Id=5(parentId=2),Id=6(parentId=3)

If Id= 6 there is no data that parentId=6 so only 6 will be return.

to find the sub data and its selft.
Jack J Jun 24,881 Reputation points Microsoft External Staff

2023-02-22T02:31:58.3133333+00:00

@打玻璃, thanks for the feedback, based on your description, we have to use recursion to do it. Also according to my test, PatriceSc's Answer is good.

However, I added the following code to consider that If Id= 6 there is no data that parentId=6 so only 6 will be return.

foreach(var testId in new string[]{"1","2","6"}) { var result=GetChildsFor(testId); if(result.Count()==0) ->added { Console.WriteLine(testId + ": " + testId); } else { Console.WriteLine(testId + ": " + string.Join(", ", result.OrderBy(o=>o))); } }
Jack J Jun 24,881 Reputation points Microsoft External Staff

2023-03-02T07:22:44.73+00:00

@打玻璃, is any update for this question?

Answer 1

Hi,

In short you want to get a single flat list with a node id as well as all its direct and indirect childs id?

Basically you'll need a recursive method that loads chidls from an id (or from a list of ids). You'll call that for the root id and each time it load childs it will call itself recursively to load childs for those childs etc... until no more childs are loaded.

Another option is to use a server side "recursive common table expression" if using SQL Server.

Edit: I created a sample at https://dotnetfiddle.net/2tULlj so that you can get the idea.

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how to get sub data in entityframework core?

1 answer

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