Selecting all child objects in Linq

Question

This really should be easy, but I just can't work it out myself, the interface is not intuitive enough... :( Let's say I have a `State` table, and I want to select all `Counties` from multiple `States`. In SQL that would be: ``` select c.* from State s join County c on c.StateCode = s.StateCode where s.TimeZone = -5 -- or some other criteria ``` The above example is trivial enough to convert to Linq in a static context: ``` var q = MyDataContext.GetTable().Where(c => c.State.TimeZone = -5); ``` But where it starts getting complicated is if I want a more context sensitive query, such as the following: ``` public static List GetCountiesForStates(List states) { // gotta do something to return all the counties for all these states } ``` Now I could do something like this inside that method: ``` var q = MyDataContext.GetTable().Where(c => states.Contains(c.State)); ``` but IMO that is really inelegant, because (a) I have to get a static `MyDataContext` instea…

Accepted Answer

You can do this:

```
var q = from c in countries
        from s in c.States
        where c.Property == Something
        select s;
```

This will give you an enumeration of all states within all countries. This translates into the following:

```
var q = countries.Where(x => c.Property == Something).SelectMany(c => c.States);
```

Selecting all child objects in Linq

Solution

Problem