/// <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>()));
}
/// <summary>
/// Returns the first collection without the common elements from both input collections.
/// </summary>
/// <param name="collection">The input collection for the except operation</param>
/// <returns>The firt collection with commmon elements removed.</returns>
public QueryCollectionValue Except(QueryCollectionValue collection)
{
var resultValues = new List <QueryValue>();
foreach (QueryValue element in this.Elements)
{
if (!collection.Elements.Any(v => this.ValuesAreEqual(v, element)))
{
resultValues.Add(element);
}
}
// except removes duplicates from the result, so applying distinct at the end
var exceptResult = new QueryCollectionValue(this.Type, this.EvaluationStrategy, QueryError.GetErrorFromValues(resultValues), resultValues);
var result = exceptResult.Distinct();
return(result);
}
