LINQ - Where not exists

Question

What is the equivalent of following statement in LINQ:

Select t1.appname, t1.julianDte, t1.cat 
From table1 t1 
Where NOT EXISTS 
   ( Select * 
     from ta         


        

Answer 1

from t1 in Context.table1DbSet
let ok = 
    (from t2 in Context.table2DbSet 
     where t2.Idt1 = t1.Idt1 && t1.DateValid.HasValue
    ).Any()
where 
   t1.Active
   && !ok