Linq2Sql IQueryable内另一个IQueryable

Question

I'm trying to structure my code and be able to better maintain some of my LINQ queries. Actually I created a new helper class with some functions but I'm having some problems executing some of my IQueryable functions inside another IQueryable functions.

When I execute the function SupplierMappings.GetSupplierAssociatedRT(int supplierID) I'm getting the following error:

Method 'System.Linq.IQueryable`1[VMPortal.DataAccessLayer.CostCentre]
GetSupplierAssociatedCCPerRT(Int32, Int32)' has no supported translation to SQL.

What I'm doing wrong? Below is the part of related code:

public class SupplierMappings
{
    private static DataLayer dl = DataLayer.GetDataContext();

    public static IQueryable<ResourceType> GetSupplierAvailableRT(int supplierID)
    {
        return dl.ResourceTypes.Where(x =>
            dl.SuppliersCompanies2.Any(y => y.SupplierID == supplierID
                && y.ResourceTypeID == x.ResourceTypeID
                && y.StatusID == (short)SuppliersCompaniesStatusEnum.Active));
    }

    public static IQueryable<ResourceType> GetSupplierAssociatedRT(int supplierID)
    {
        return GetSupplierAvailableRT(supplierID).Where(x =>
            // Check if we have at least one CC associated with that RT
            GetSupplierAssociatedCCPerRT(supplierID, x.ResourceTypeID).Count() >= 1);
    }

    public static IQueryable<CostCentre> GetSupplierAvailableCCPerRT(int supplierID, int rtID)
    {
        return dl.CostCentres.Where(x => x.StatusID == (short)CostCentersStatusEnum.Active
            // Check than the supplier is mapped at supplier level at same company & RT
            && dl.SuppliersCompanies2.Any(y => y.CompanyID == x.CompanyID
                && y.SupplierID == supplierID
                && y.ResourceTypeID == rtID
                && y.StatusID == (short)SuppliersCompaniesStatusEnum.Active)
            // Check than the PA is active
            && x.DeliveryGroup.StatusID == (short)DeliveryGroupsStatusEnum.Active);
    }

    public static IQueryable<CostCentre> GetSupplierAssociatedCCPerRT(int supplierID, int rtID)
    {
        return GetSupplierAvailableCCPerRT(supplierID, rtID).Where(x =>
            dl.SuppliersCostCentre2.Count(y => y.SupplierID == supplierID
                && y.StatusID == (short)SuppliersCostCentreStatusEnum.Inactive
                && y.ResourceTypeID == rtID) != dl.SuppliersCompanies2.Count(y => y.SupplierID == supplierID
                    && x.CompanyID == y.CompanyID
                    && y.StatusID == (short)SuppliersCompaniesStatusEnum.Active
                    && y.ResourceTypeID == rtID)
            && dl.SuppliersPracticeAreas.Count(y => y.SupplierID == supplierID
                && y.StatusID == (short)SuppliersPracticeAreaStatusEnum.Inactive
                && y.ResourceTypeID == rtID) != dl.SuppliersCompanies2.Count(y => y.SupplierID == supplierID
                    && x.CompanyID == y.CompanyID
                    && y.StatusID == (short)SuppliersCompaniesStatusEnum.Active
                    && y.ResourceTypeID == rtID));
    }
}

Answer 1

It is pity but in linq to sql you cannot use you defined methods that returns anything except expressions. And there is limited number of expressions that can be translated to sql query (this translations is defined in linqtosql library). So you cannot do what you try to do. You could try to inline your functions.