Perform calculation inside select statement in LINQ

Question

I have a situation where i have to calculate percentage of two values for example

IEnumerable result = 
    from r in renewalLists
    gro         


        

Answer 1

If you're wanting to pull values from the original query, and then populate an additional property, you can do it like this:

        IEnumerable result =
            (from r in renewalLists
            group r by r.CityID into grpCity
            select new RenewalModel
            {
                CityID = grpCity.Key,
                City = (from g in grpCity where g.CityID == grpCity.Key select g.City).First().Trim(),
                PotentialRenewalCount = (from g in grpCity where g.CityID == grpCity.Key select g.PotentialRenewalCount).Sum(),
                PotentialRenewalSQRT = (from g in grpCity where g.CityID == grpCity.Key select g.PotentialRenewalSQRT).Sum(),
                RENEWALCOUNT = (from g in grpCity where g.CityID == grpCity.Key select g.RENEWALCOUNT).Sum(),
                RENEWALSQRT = (from g in grpCity where g.CityID == grpCity.Key select g.RENEWALSQRT).Sum()
            }).select(r => new RenewalModel
            {
                desiredCalucation = (r.PotentialRenewalCount / r.PotentialRenewalCount) * 100,
                CityID = r.CityID,
                City = r.City,
                PotentialRenewalCount = r.PotentialRenewalCount,
                PotentialRenewalSQRT = r.PotentialRenewalSQRT,
                RENEWALCOUNT = r.RENEWALCOUNT,
                RENEWALSQRT = r.RENEWALSQRT
            });

Seems like you're doing an lot of "requerying" the same record in the individual assignments, though. You could probably accomplish the same thing in a much cleaner way by using a "join" on CityID.

Remember, that LINQ also supports subqueries:

        IEnumerable result =
            (from g in (
                from r in renewalList
                join c in cityList on r.CityID equals c.CityID
                select new RenewalModel
                {
                    CityID = grpCity.Key,
                    City = (from g in grpCity where g.CityID == grpCity.Key select g.City).First().Trim(),
                    PotentialRenewalCount = (from g in grpCity where g.CityID == grpCity.Key select g.PotentialRenewalCount).Sum(),
                    PotentialRenewalSQRT = (from g in grpCity where g.CityID == grpCity.Key select g.PotentialRenewalSQRT).Sum(),
                    RENEWALCOUNT = (from g in grpCity where g.CityID == grpCity.Key select g.RENEWALCOUNT).Sum(),
                    RENEWALSQRT = (from g in grpCity where g.CityID == grpCity.Key select g.RENEWALSQRT).Sum()
                })
            group g by g.CityID into grpCity
            select new RenewalModel
            {
                desiredCalucation = (g.PotentialRenewalCount / g.PotentialRenewalCount) * 100,
                CityID = g.CityID,
                City = g.City.Trim(),
                PotentialRenewalCount = g.PotentialRenewalCount.Sum(),
                PotentialRenewalSQRT = g.PotentialRenewalSQRT.Sum(),
                RENEWALCOUNT = g.RENEWALCOUNT.Sum(),
                RENEWALSQRT = g.RENEWALSQRT.Sum()
            });