private static IEnumerable <double> ToNumbers(ValueDescriptor descriptor, CultureInfo culture, IEnumerable <object> values)
{
return(values
.Select(x => ValueConversions.ToNumber(descriptor, culture, x))
.Where(x => x.HasValue)
.Select(x => x.Value));
}
private object Aggregate(DataSet dataset, ValueDescriptor descriptor, IEnumerable <object> values)
{
Debug.Assert(descriptor != null);
Debug.Assert(values != null);
Debug.Assert(_accumulator.IsEmpty || _culture != null);
if (!String.IsNullOrWhiteSpace(descriptor.AggregationExpression))
{
var evaluator = new ExpressionEvaluator(dataset);
evaluator.AddConstant(ExpressionEvaluator.IdentifierValues, values);
return(evaluator.Evaluate(() => descriptor.AggregationExpression));
}
// TODO: AggregationMode.None may be checked at the very beginning, no need to create a
// list of values if there is nothing to do with them...
if (descriptor.PreferredAggregation == AggregationMode.None)
{
return(null);
}
if (descriptor.PreferredAggregation == AggregationMode.Count)
{
return(values.Count());
}
var numbers = values
.Select(x => ValueConversions.ToNumber(descriptor, _culture, x))
.Where(x => x.HasValue);
// Sum of an empty set is zero but average is null
if (descriptor.PreferredAggregation == AggregationMode.Sum)
{
return(numbers.Sum());
}
if (descriptor.PreferredAggregation == AggregationMode.Average)
{
return(numbers.Any() ? (object)(numbers.Sum() / numbers.Count()) : null);
}
throw new NotSupportedException();
}