How can do in LinqToSql an equivalent to the IN clause?

I have a SQL statement like this:

```sql
select *
from funktion 
where institution_id IN (select id from institution where kreis_id = 36)

```

How can I express that in a Linq-to-Sql statement?

For explanation: the table `funktion` is something like `CAPACITY` and the table `institution` is representing INSTITUTIONS with hierarchy structure.

Every function is referenced between the tables with `institution.id == funktion.institution_id`. The hierarchy structures are from high to low: VERBAND, BEZIRK, KREIS, VEREIN.

Every VERBAND consists of several BEZIRK. Each BEZIRK consist of several KREIS. Each KREIS consist of several VEREIN. Every Hierarchy-layer has its ID for lower layers in referenced ID columns. So the lowest layer has a beside its own ID (Primary Key) a column for KREIS\_ID, BEZIRK\_ID, VERBAND\_ID to know to which next levels it belongs. So I have to make statements for each layer to see the functions of all lower levels.

In my SQL example shown earlier, I have a `KREIS` that needs to get all `FUNCTIONS` where the `INSTITUTION_ID` is in a select of IDS where the `KREIS_ID` is like the `OWN_ID` (here for example 36).

I hope someone could help me. I am very new in LINQ, ,but have to change old software structures to a newer DataSource.