Linq Select Group By

Question

I have the following class structure    public class PriceLog      public DateTime LogDateTime  get  set      public int Price  get  set       For a List lt  PriceLog   I want a Linq query to generate an output which is equivalent to the data represented as below   LogDateTime   AVG Price  Jan 2012      2000 Feb 2012      3000  Simply   I want to compute the average price over each month of the year  Note  LogDateTime property should be formatted as LogDateTime ToString  MMM yyyy    I have tried the following  but not sure whether it will generate the desired result   var result   from priceLog in PriceLogList                          group priceLog by priceLog LogDateTime ToString  MMM yyyy   into dateGroup                          select new PriceLog   GoldPrice    int dateGroup Average p   gt  p GoldPrice   SilverPrice    int dateGroup Average p   gt  p SilverPrice

User · Accepted Answer

This will give you sequence of anonymous objects, containing date string and two properties with average price:

var query = from p in PriceLogList
            group p by p.LogDateTime.ToString("MMM yyyy") into g
            select new { 
               LogDate = g.Key,
               AvgGoldPrice = (int)g.Average(x => x.GoldPrice), 
               AvgSilverPrice = (int)g.Average(x => x.SilverPrice)
            };

If you need to get list of PriceLog objects:

var query = from p in PriceLogList
            group p by p.LogDateTime.ToString("MMM yyyy") into g
            select new PriceLog { 
               LogDateTime = DateTime.Parse(g.Key),
               GoldPrice = (int)g.Average(x => x.GoldPrice), 
               SilverPrice = (int)g.Average(x => x.SilverPrice)
            };

User · Answer

var result   priceLog GroupBy s   gt  s LogDateTime ToString  MMM yyyy    Select grp   gt  new PriceLog     LogDateTime   Convert ToDateTime grp Key   Price    int grp Average p   gt  p Price     ToList      I have converted it to int because my Price field was int and Average method return double  I hope this will help

User · Answer

You should try it like this   var result           from priceLog in PriceLogList         group priceLog by priceLog LogDateTime ToString  MMM yyyy   into dateGroup         select new               LogDateTime   dateGroup Key              AvgPrice   dateGroup Average priceLog   gt  priceLog Price

User · Answer

from p in PriceLog     group p by p LogDateTime ToString  MMM   into g     select new                 LogDate   g Key ToString  MMM yyyy            GoldPrice    int dateGroup Average p   gt  p GoldPrice            SilverPrice    int dateGroup Average p   gt  p SilverPrice

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