How to flatten a GroupBy and select in linq

Question

I have a query that's returning some grouped data, and I'm drawing a blank on how to "flatten" it so that top level information is available at each group.

Account A
    - Group A
    - Group B
    - Group C
    - etc

Account B
    - Group B
    - Group C

What I want to do is "flatten" this to:

Account A | Group A | Sum(Group)
Account A | Group B | Sum(Group)
Account A | Group C | Sum(Group)
Account B | Group B | Sum(Group)
Account B | Group C | Sum(Group)

Here's what I have so far, but I'm not totally sure where to go

var transactions = Accounts.Where(clause)
    .Select(x => new
    {
        Account = x,
        TransGroupedByBucket = x.TransactionLogs.GroupBy(tl => tl.TransactionType.BucketTypeID)
    })

    //pseudocode
    //Select  new {
    //   Account,
    //   One_TransactionLog_Group
    //}

    //will run for each group:
    .Select(x => new
    {
        AccountInfo = x.Account.ID
        Sum = One_TransactionLog_Group.Sum(tl => tl.Amount)
    })
    ;

I think I'm just having a brain fart, can someone point me in the right direction? One idea I had was to flip it to start at the TransactionLog level and traverse to the Account, but there might be 0 TransactionLogs for an Account, so that might not work properly.

Answer 1

You could use SelectMany:

Accounts.SelectMany(x => x.TransactionLogs.
                           Select(y => new { Account = x.ID,
                                             TransactionLog = y,
                                             Sum = ... });