LinqtoSql Pre-compile Query problem with Count() on a group by

Question

Have a LinqtoSql query that I now want to precompile.

var unorderedc =
            from insp in sq.Inspections
            where insp.TestTimeStamp > dStartTime && insp.TestTimeStamp < dEndTime
                && insp.Model == "EP" && insp.TestResults != "P"
            group insp by new { insp.TestResults, insp.FailStep } into grp

            select new
            {

                FailedCount = (grp.Key.TestResults == "F" ? grp.Count() : 0),
                CancelCount = (grp.Key.TestResults == "C" ? grp.Count() : 0),
                grp.Key.TestResults,
                grp.Key.FailStep,
                PercentFailed = Convert.ToDecimal(1.0 * grp.Count() / tcount * 100)

            };

I have created this delegate:

public static readonly Funct<SQLDataDataContext, int, string, string, DateTime, DateTime, IQueryable<CalcFailedTestResult>>
    GetInspData = CompiledQuery.Compile((SQLDataDataContext sq, int tcount, string strModel, string strTest, DateTime dStartTime,
    DateTime dEndTime, IQueryable<CalcFailedTestResult> CalcFailed) =>
    from insp in sq.Inspections
            where insp.TestTimeStamp > dStartTime && insp.TestTimeStamp < dEndTime
                && insp.Model == strModel && insp.TestResults != strTest
            group insp by new { insp.TestResults, insp.FailStep } into grp
            select new 
            {
                FailedCount = (grp.Key.TestResults == "F" ? grp.Count() : 0),
                CancelCount = (grp.Key.TestResults == "C" ? grp.Count() : 0),
                grp.Key.TestResults,
                grp.Key.FailStep,
                PercentFailed = Convert.ToDecimal(1.0 * grp.Count() / tcount * 100)
            });

The syntax error is on the CompileQuery.Compile() statement

It appears to be related to the use of the select new {} syntax. In other pre-compiled queries I have written I have had to just use the select projection by it self. In this case I need to perform the grp.count() and the immediate if logic.

I have searched SO and other references but cannot find the answer.

Answer 1

In short, you can't have a CompliedQuery for an anonymous type, you need to have the query return a named type, so your

select new 
        {
            FailedCount = (grp.Key.TestResults == "F" ? grp.Count() : 0),
            CancelCount = (grp.Key.TestResults == "C" ? grp.Count() : 0),
            grp.Key.TestResults,
            grp.Key.FailStep,
            PercentFailed = Convert.ToDecimal(1.0 * grp.Count() / tcount * 100)
        }

Would now be:

select new MyType
        {
            FailedCount = (grp.Key.TestResults == "F" ? grp.Count() : 0),
            CancelCount = (grp.Key.TestResults == "C" ? grp.Count() : 0),
            TestResults = grp.Key.TestResults,
            FailStep = grp.Key.FailStep,
            PercentFailed = Convert.ToDecimal(1.0 * grp.Count() / tcount * 100)
        }

The last generic param of your Func<> would be IQueryable<MyType> as well, since that's what your query would now return.

In this case, MyType would look something like:

public class MyType {
  public int FailedCount { get; set; }
  public int CancelCount { get; set; }
  public string TestResults { get; set; }
  public string FailStep { get; set; } //Unsure of type here
  public decimal PercentFailed { get; set; }
}