Question

Building a bunch of reports, have to do the same thing over and over with different fields

    public List<ReportSummary> ListProducer()
    {
        return (from p in Context.stdReports                    
                group p by new { p.txt_company, p.int_agencyId }
                    into g
                    select new ReportSummary
                    {
                        PKi = g.Key.int_agencyId,
                        Name = g.Key.txt_company,
                        Sum = g.Sum(foo => foo.lng_premium),
                        Count = g.Count()
                    }).OrderBy(q => q.Name).ToList();
    }

    public List<ReportSummary> ListCarrier()
    {
        return (from p in Context.stdReports
                group p by new { p.txt_carrier, p.int_carrierId }
                    into g
                    select new ReportSummary
                    {
                        PKi = g.Key.int_carrierId,
                        Name = g.Key.txt_carrier,
                        Sum = g.Sum(foo => foo.lng_premium),
                        Count = g.Count()
                    }).OrderBy(q => q.Name).ToList();
    }

My Mind is drawing a blank on how i might be able to bring these two together.

Answer 1

Since all that changes between the two queries is the group key, parameterize it. Since it’s a composite key (has more than one value within), you’ll need to create a simple class which can hold those values (with generic names).

In this case, to parameterize it, make the key selector a parameter to your function. It would have to be an expression and the method syntax to get this to work. You could then generalize it into a function:

public class GroupKey
{
    public int Id { get; set; }
    public string Name { get; set; }
}

private IQueryable<ReportSummary> GetReport(
    Expression<Func<stdReport, GroupKey>> groupKeySelector)
{
    return Context.stdReports
        .GroupBy(groupKeySelector)
        .Select(g => new ReportSummary
        {
            PKi = g.Key.Id,
            Name = g.Key.Name,
            Sum = g.Sum(report => report.lng_premium),
            Count = g.Count(),
        })
        .OrderBy(summary => summary.Name);
}

Then just make use of this function in your queries using the appropriate key selectors.

public List<ReportSummary> ListProducer()
{
    return GetReport(r =>
        new GroupKey
        {
            Id = r.int_agencyId,
            Name = r.txt_company,
        })
        .ToList();
}

public List<ReportSummary> ListCarrier()
{
    return GetReport(r =>
        new GroupKey
        {
            Id = r.int_carrierId,
            Name = r.txt_carrier,
        })
        .ToList();
}

I don’t know what types you have mapped for your entities so I made some assumptions. Use whatever is appropriate in your case.