An implicitly-typed local variable cannot be set to void.

• ForEach() has type void.

• Select() returns IEnumerable<T>, ToList() returns List<T>, etc.

so:

List<X> x = ...Select(x => x).ToList(); // List<T>

or

x.ForEach(x => x); // void

because you can't assign void to List<T>.

var query = rep.GetIp()  // in this line i have the error
           .Where(x => x.CITY == CITY)
           .GroupBy(y => o.Fam)
           .Select(z => new IpDTO
                        {
                            IId = z.Key.Id,
                            IP = z.Select(x => x.IP).Distinct()
                        });

foreach (var dto in query)
{
    foreach (var ip in dto.IP)
    {
        PAINTIP(ip);
    }
}

or

var query = ....
           .SelectMany(z => z.Select(x => x.IP).Distinct());

foreach (var ip in query)
{
    PAINTIP(ip);
}