using System;

public class Program

{

    public static void Main()

    {

        int[] CoAIds = new[]{ 1,2,3 };

        var first = FirstApproach(CoAIds);

        var second = FirstApproach(CoAIds);

    }

​

     private static int FirstApproach(int[] CoAIds){

        decimal[] data = null;

​

        using (Entities dataContext = new Entities())

        {

                data = (from fs in dataContext.FinancialStatementResults

                            where fs.OrgId == OrgId

                            join xs in CoAIds on fs.CoAId equals xs

                            where fs.PlanId == PlanId

                            where fs.Year == Year

                            select fs.Amount 

                        ).ToArray();

         }

         var summed = (int)data.Sum();

         return summed;

     }

​

     private static int SecondApproach(int[] CoAIds){

​

        using (Entities dataContext = new Entities())

        {

             decimal[] data = dataContext.FinancialStatementResults

                        .Where(fs=> fs.OrgId == OrgId && s.PlanId == PlanId && fs.Year == Year)

                        .Where(fs=> CoAIds.Contains(fs.CoAId))

                        .Select(fs.Amount)

                        .ToArray();

              var summed = (int)data.Sum();

              return summed;

         }

     }

}