var users = new 
    {
        AgeLessThan30 = db.Users.Select(x => x.Age < 30),
        AgeEqualAndGreaterThan30 = db.Users.Select(x => x.Age >= 30),
        Total = db.Users
    }

------解决方案--------------------
C# code
var users = new 
    {
        AgeLessThan30 = db.Users.Where(x => x.Age < 30),
        AgeEqualAndGreaterThan30 = db.Users.Where(x => x.Age >= 30),
        Total = db.Users
    };

------解决方案--------------------
举个例子来看看

------解决方案--------------------
LINQ中分组求和
from r in Repairs
group r by r.VIN into grouped
select new
{
VIN = grouped.Key,
TotalCost = grouped.Sum(c => c.Cost)
};
楼主到底是想实现什么效果，最好给出具体的需求。