LINQ using dictionary in where clause

Question

er have the following query in linq...

Whenever I try to run it I get a No comparison operator for type System.Int[] exception.

It's got something to do with the dictionary I am sure, but I don't understand why this isn't valid and was wondering if someone could explain?

// As requested... not sure it will help though.
var per = (
    from p in OtherContext.tblPeriod 
    where activeContractList.Select(c => c.DomainSetExtensionCode).Contains(p.DomainSetExtensionCode) 
    select p).ToArray();

var com = (
    from c in MyContext.tblService 
    join sce in MyContext.tblServiceExtension
    on c.ServiceExtensionCode equals sce.ServiceExtensionCode
    join sc in MyContext.tblServiceContract
    on sce.ServiceContractCode equals sc.ContractCode
    group sc by c.Period into comG
    select new
    {
        PeriodNumber = comG.Key,
        Group = comG,
    }).ToArray();

var code =
    (from c in com
    join p in per on c.PeriodNumber equals p.PeriodNumber
    select new
    {
        p.Code, 
        c.Group
    }).ToArray();

var payDictionary = new Dictionary<int, int[]>();

// This is another linq query that returns an anonymous type with
// two properties, and int and an array.
code.ForEach(c => payDictionary.Add(c.Code, c.Group.Select(g => g.Code).ToArray()));

// MyContext is a LINQ to SQL DataContext
var stuff = (
from
    p in MyContext.tblPaySomething
    join cae in MyContext.tblSomethingElse
    on p.PaymentCode equals cae.PaymentCode
    join ca in MyContext.tblAnotherThing
    on cae.SomeCode equals ca.SomeCode
where
    // ca.ContractCode.Value in an int?, that should always have a value.
    payDictionary[p.Code].Contains(ca.ContractCode.Value)
select new
{
    p.Code,
    p.ExtensionCode,
    p.IsFlagged,
    p.Narrative,
    p.PayCode,
    ca.BookCode,
    cae.Status
}).ToList();

Answer 1

You won't be able to do this with a dictionary. The alternative is to join the three linq queries into one. You can do this with minimal impact to your code by not materializing the queries with ToArray . This will leave com and code as IQueryable<T> and allow for you compose other queries with them.

You will also need to use a group rather than constructing a dictionary. Something like this should work:

var per = (
    from p in OtherContext.tblPeriod 
    where activeContractList.Select(c => c.DomainSetExtensionCode).Contains(p.DomainSetExtensionCode) 
    select p.PeriodNumber).ToArray(); // Leave this ToArray because it's materialized from OtherContext

var com = 
    from c in MyContext.tblService 
    join sce in MyContext.tblServiceExtension on c.ServiceExtensionCode equals sce.ServiceExtensionCode
    join sc in MyContext.tblServiceContract on sce.ServiceContractCode equals sc.ContractCode
    group sc by c.Period into comG
    select new
    {
        PeriodNumber = comG.Key,
        Group = comG,
    }; // no ToArray

var code =
    from c in com
    where per.Contains(c.PeriodNumber) // have to change this line because per comes from OtherContext
    select new
    {
        Code = c.PeriodNumber, 
        c.Group
    }; // no ToArray

var results = 
    (from p in MyContext.tblPaySomething
     join cae in MyContext.tblSomethingElse on p.PaymentCode equals cae.PaymentCode
     join ca in MyContext.tblAnothThing on cae.SomeCode equals ca.SomeCode
     join cg in MyContext.Codes.GroupBy(c => c.Code, c => c.Code) on cg.Key equals p.Code
     where cg.Contains(ca.ContractCode.Value)
     select new
     {
         p.ContractPeriodCode,
         p.DomainSetExtensionCode,
         p.IsFlagged,
         p.Narrative,
         p.PaymentCode,
         ca.BookingCode,
         cae.Status
     })
    .ToList();

Side Note: I also suggest using navigation properties where possible instead of joins. It makes it much easier to read and understand how objects are related and create complex queries.