/// <summary>
/// Groups elements using key computed from the key selector.
/// </summary>
/// <param name="keySelector">Key selector lambda.</param>
/// <returns>Elements grouped based on the provided key.</returns>
public QueryCollectionValue GroupBy(Func <QueryValue, QueryValue> keySelector)
{
if (this.IsNull)
{
return(new QueryCollectionValue(this.Type.ElementType.CreateCollectionType(), this.EvaluationStrategy, this.EvaluationError, null));
}
var keys = this.Elements.Select(keySelector).ToList();
var keyCollection = new QueryCollectionValue(this.Type.ElementType.CreateCollectionType(), this.EvaluationStrategy, this.EvaluationError, keys);
var distinctKeys = keyCollection.Distinct().Elements;
var elementType = this.Type.ElementType;
var groupings = distinctKeys.Select(key =>
{
if (key.IsNull)
{
var matchingNullElements = this.Elements.Where(element => keySelector(element).IsNull);
return(this.CreateGroupingValue(key, QueryCollectionValue.Create(elementType, matchingNullElements.ToArray())));
}
else
{
return(this.CreateGroupingValue(key, QueryCollectionValue.Create(elementType, this.Elements.Where(element => this.ValuesAreEqual(keySelector(element), key)).ToArray())));
}
});
var keyType = keySelector(elementType.NullValue).Type;
var groupingType = new QueryGroupingType(keyType, elementType, this.EvaluationStrategy);
return(new QueryCollectionValue(groupingType.CreateCollectionType(), this.EvaluationStrategy, QueryError.GetErrorFromValues(groupings), groupings.Cast <QueryValue>()));
}
private QueryStructuralValue CreateGroupingValue(QueryValue key, QueryCollectionValue elements)
{
QueryGroupingType groupingType = new QueryGroupingType(key.Type, elements.Type.ElementType, key.Type.EvaluationStrategy);
var error = QueryError.GetErrorFromValues(elements.Elements.Concat(new[] { key }));
var result = new QueryStructuralValue(groupingType, false, error, groupingType.EvaluationStrategy);
result.SetValue("Key", key);
result.SetValue("Elements", elements);
return(result);
}