Linq hierarchy drill down from table values

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C#

LINQ

MVC5

ASP.NET5

I have two tables, one an invoice table and the other a hierarchy table for the accounts on the invoice

Invoice Table:

| InvoiceNo| AccNo| InvoiceAmount |
    --------------------------------------
    | A1234| 345| 100.00   |
    | A1235| 346| 95.00    |
    | A1236| 347| 15.50    |
    | A1237| 348| 20.10    |

Hierarchy Table

| AccNo| HierAccNo| Level|
    --------------------------------------
    | 123|    | 1    |
    | 789| 123| 2    |
    | 890| 123| 2    |
    | 345| 789| 3    |
    | 346| 789| 3    |
    | 347| 890| 3    |
    | 348| 890| 3    |

What I'm trying to do is to roll up the amounts from the invoice table to the highest level AccNo which is Level1 and then on a seperate instance from the highest account number roll back down to the next levels.

What I have tried:

So far I am able to roll up to the highest band number by the following :

var BandL2 = from invoice in db.Invoices//Roll up to level 2
                             join ban in db.HierarchyTable
                             on invoice.AccNo equals ban.Ban
                             where invoice.GlobalInvoiceID == globalInvoice.Id
                             group invoice by ban.HierAccNo into bandHierarchy
                             select new
                             {
                                 Level2Band = bandHierarchy.Key,
                                 Amount = bandHierarchy.Sum(m=> m.InvoiceAmount)
                             };

                var bandHierarchyTable = db.HierarchyTable.AsQueryable();

                var BandL1 = from band2 in BandL2 // Roll Up to level 1
                             join band1 in bandHierarchyTable
                             on band2.Level2Band equals band1.Ban
                             group band2 by band1.HierAccNo into bandL1
                             select new
                             {
                                 Level1Band = bandL1.Key,
                                 Amount = bandL1.Sum(m => m.Amount)
                             };

But now I'm having an issue reversing the process and drilling down from Level 1 as the only details from the form is the AccNo of Level 1(eg. 123).
I'm trying to do this on the fly using pop up modals as I'm drilling.

How do I drill down again so that I can get level by level amounts?
Example:

Ouput Table from Above Code

| AccNo| Amount|
    --------------------------------------
    | 123| 230.60 |

Then

| AccNo| Amount|
    -------------------------------------- 
    | 789| 195  | 
    | 890| 35.60|

And then clicking on one of the AccNo.

| AccNo| Amount|
    -------------------------------------- 
    | 345| 100| 
    | 346| 95 |

Thanks!