Linq query in controller for selecting fields in database

Yes, it is possible:

Controller:

List<MyType> data= GetStuffFromLinqHere();
viewBag.DropDownSelectList = 
    new SelectList( 
        data      
        "IDPropertyName", 
        "DisplayPropertyName", 
        data.FirstOrDefaut()/*Select the first Item by default (optional)*/    ); 

View, where you want the list::

@Html.DropDownListFor( model => ViewBag.ValueYouWantTheSelectedValueToBeIn, ViewBag.DropDownSelectList)

Obviously, I can't give meaningful names as I don't know what your are doing exactly. IDPropertyName is the name of the property you want in the Id of the list item, similarly DisplayPropertyName is the name of the property you want to display in the DDL. ValueYouWantTheSelectedValueToBeIn is where you want the selected value to be placed when the form is submitted.

Additionally, you may have a view model, in which case don't used the ViewBag any you should sort the List either in or after the GetStuffFromLinqHere() method call. If you have a complex id or description, you should either create a view model to handle it, or add a property to the type the Linq contains in the list.