Ignore the null parameter in a Linq query

Hi, I have a Json in a controller that filters my view, the issue is that sometimes receives some of the parameters in Null and does not return records as I could do to ignore me if the parameter enters as null?

This is the code:

public JsonResult filtro( int? loca, int? barrio, int? tipo)
    {


        var r = (from e in db.Inmuebles.Include(a => a.Barrios.Localidades).Include(a => a.Barrios).Include(a => a.Imagenes).Include(a => a.Tipo_Inmuebles)
                 where e.Barrios.cod_localidad == loca
                 where e.cod_tipo_inmueble == tipo
                 where e.cod_barrio == barrio
                 select new InmoVista
                 {
                     barrio = e.Barrios.barrio,
                     localidad = e.Barrios.Localidades.localidad,
                     codigo = e.cod_inmueble,
                     tipo = e.Tipo_Inmuebles.tipo_inmueble,
                     calle = e.calle,
                     numero = e.numero,
                     descripcion = e.descripcion
                 }).ToList();