linq query to get child items through self referencing join table

Question

I have 2 SQL Server tables. A parent can have many children as detailed below. In this case - John smith has one child (Lisa Smith) by the relationship

People
|---------------|------------|
|   PersonID    |    Name    |
|---------------|------------|
|       1       | John Smith |
|---------------|------------|
|       2       | Lisa Smith |
|---------------|------------|

Details
|---------------|---------------|---------------|---------------|
|   DetailsID   |   PersonID    | DetailsType   | ParentID      |
|               |               |               |(ref DetailsID)|
|---------------|---------------|---------------|---------------|
|    1001       |1 (John Smith) | parent        | NULL          |
|---------------|---------------|---------------|---------------|
|    1002       |2 (Lisa Smith) | child         | 1001          |
|---------------|---------------|---------------|---------------|

In a SQL Query I would get John's children by the DetailsID like this (I already have DetailsID in the code at this point)

SELECT p.Name
    FROM People p
    JOIN Details d on d.PersonID = p.PersonID
    WHERE ParentID = 1001

In my C# project I know how to get the list of ParentIDs in the Details table by the DetailsID but I don't know how to get the children's details. this is what I have in my mapping:

Children = (from d in dbSource.Details
            where d.ParentID == 'the DetailID for parent that I have'
            select d.PersonId).ToList())

This will return a list of the Childrens' IDs but I need to return a list of objects containing all children's details from the People table.

Thanks in advance.

Answer 1

You can use join-clasue to fetch the People data

Children = ( from p in dbSource.People 
             join d in dbSource.Details
             on p.PersonID equals d.PersonID 
             where d.ParentID == 'the DetailID for parent that I have'
            select p
            ).ToList())

Answer 2

You have to try join the tables using join clause try the following query

var Children = from p in dbSource.People
               join d in dbSource.Details
               on p.PersonId equals d.PersonId
               where d.ParentId == 123 select new 
               {PersonId = p.PersonId, PersonName = p.Name};