LINQ - Get all items in a List within a List?

Question

I'm currently working my way through the learning curve that is LINQ and I could really use some assistance. I don't know if what I want is possible, but if I had to wager, I bet it is.

I currently have a list of objects called _tables and each of these objects has within it another list of objects exposed through the property, "Indexes". Essentially, I'd like to end up with one List that contains all the Indexes from all of the _tables.

Here's what I have so far:

var indexes = from TableInfo tab
              in _tables
              where tab.Indexes.Count > 0
              select tab.Indexes;

Unfortunately, this seems to be giving me another List of Lists, but only where the Indexes List contains more than one value... Is there some way to get all of these lists together without loops?

Answer 1

您想使用SelectMany扩展方法。

_tables.SelectMany(t => t.Indexes)

Answer 2

In addition to tbischel's answer, the query expression version of what you're going for is below.

var indexes = from TableInfo tab in _tables 
              from index in tab.Indexes
              select index;

Answer 3

You don't need the where clause and you also shouldn't need to tell it what tab is

And you will need to use SelectMany

var indexes = (from tab in _tables).SelectMany(t => t.Indexes)

Or you could do it like this

   var indexes = from tab in _tables
                  from t in tab.Indexes
                  select t;

That should be a little more familiar syntaz

Answer 4

var rows = from item in table select item;