// new CollectionWrapper<ElementType> { Instance = source.Select((ElementType element) => new Wrapper { }) }
private Expression ProjectCollection(Expression source, Type elementType, SelectExpandClause selectExpandClause, IEdmEntityType entityType, IEdmEntitySet entitySet, ExpandedNavigationSelectItem expandedItem)
{
ParameterExpression element = Expression.Parameter(elementType);
// expression
// new Wrapper { }
Expression projection = ProjectElement(element, selectExpandClause, entityType, entitySet);
// expression
// (ElementType element) => new Wrapper { }
LambdaExpression selector = Expression.Lambda(projection, element);
if (expandedItem != null)
{
source = AddOrderByQueryForSource(source, expandedItem.OrderByOption, elementType);
}
if (_settings.PageSize.HasValue || (expandedItem != null && (expandedItem.TopOption.HasValue || expandedItem.SkipOption.HasValue)))
{
// nested paging. Need to apply order by first, and take one more than page size as we need to know
// whether the collection was truncated or not while generating next page links.
IEnumerable <IEdmStructuralProperty> properties =
entityType.Key().Any()
? entityType.Key()
: entityType
.StructuralProperties()
.Where(property => property.Type.IsPrimitive() && !property.Type.IsStream())
.OrderBy(property => property.Name);
if (expandedItem == null || expandedItem.OrderByOption == null)
{
bool alreadyOrdered = false;
foreach (var prop in properties)
{
source = ExpressionHelpers.OrderByPropertyExpression(source, prop.Name, elementType,
alreadyOrdered);
if (!alreadyOrdered)
{
alreadyOrdered = true;
}
}
}
if (expandedItem != null && expandedItem.SkipOption.HasValue)
{
Contract.Assert(expandedItem.SkipOption.Value <= Int32.MaxValue);
source = ExpressionHelpers.Skip(source, (int)expandedItem.SkipOption.Value, elementType,
_settings.EnableConstantParameterization);
}
if (expandedItem != null && expandedItem.TopOption.HasValue)
{
Contract.Assert(expandedItem.TopOption.Value <= Int32.MaxValue);
source = ExpressionHelpers.Take(source, (int)expandedItem.TopOption.Value, elementType,
_settings.EnableConstantParameterization);
}
source = ExpressionHelpers.Take(source, _settings.PageSize.Value + 1, elementType, _settings.EnableConstantParameterization);
}
// expression
// source.Select((ElementType element) => new Wrapper { })
Expression selectedExpresion = Expression.Call(GetSelectMethod(elementType, projection.Type), source, selector);
if (!source.Type.IsCollection())
{
if (_settings.HandleNullPropagation == HandleNullPropagationOption.True)
{
// source == null ? null : projectedCollection
return(Expression.Condition(
test: Expression.Equal(source, Expression.Constant(null)),
ifTrue: Expression.Constant(null, selectedExpresion.Type),
ifFalse: selectedExpresion));
}
else
{
return(selectedExpresion);
}
}
else
{
return(selectedExpresion);
}
}
