LINQ to Entities Question - All objects where all items in subcollection appear in another collection?

Question

Hey all,

Hopefully I can explain this to where it make sense, but I'm trying to get a list of objects out of a master list using a speicific and complex (complex to me, at least) set of criteria.

I have a Class called TableInfo that exposes a List of ForeignKeyInfo. ForeignKeyInfo has a string property (among others) called, Table. I need to do some sequential processing using my TableInfo objects but only work with the TableInfo objects I haven't yet processed. To keep track of which TableInfo objects have already been processed I have a List which stores the name of the table after the processing has been complete.

I want to loop until all of the items in my TableInfo collection appear in my processed list. For each iteration of the loop, I should be processing all of the TableInfo items where all of the ForeignKeyInfo.Table strings appear in my processed List.

Here's how I've written it in "standard" looping code:

while(processed.Count != _tables.Count)
{
     List<TableInfo> thisIteration = new List<TableInfo>();

     foreach (TableInfo tab in _tables)
     {
          bool allFound = true;
          foreach (ForeignKeyInfo fk in tab.ForeignKeys)
          {
               allFound = allFound && processed.Contains(fk.Table);
          }

          if (allFound && !processed.Contains(tab.Name))
          {
               thisIteration.Add(tab);
          }
     }

     //now do processing using thisIteration list
     //variable, "thisIteration", is what I'd like to replace with the result from LINQ
}

Answer 1

I'm not really sure what you're trying to do here. However, you can convert the body of your loop into the following LINQ query, if that makes things simpler...

List<TableInfo> thisIteration = (from tab in _tables
                                 let allFound = tab.ForeignKeys.Aggregate(true, (current, fk) => current && processed.Contains(fk.Table))
                                 where allFound && !processed.Contains(tab.Name)
                                 select tab).ToList();

Answer 2

This should do it:

var thisIteration = _tables.Where(t => !processed.Contains(t.Name)
                                    && t.ForeignKeys
                                        .All(fk => processed.Contains(fk.Table));

I'm assuming you just need to iterate over the thisIteration collection, in which case leaving it as an IEnumerable is fine. If you need it to be a list, you can just put in a .ToList() call at the end.