private MethodCallExpression ApplyGroupBy(Expression source, GroupByTransformationNode transformation)
{
Type sourceType = OeExpressionHelper.GetCollectionItemType(source.Type);
ParameterExpression sourceParameter = Expression.Parameter(sourceType);
var visitor = CreateVisitor(sourceParameter);
var expressions = new List <Expression>();
foreach (GroupByPropertyNode node in transformation.GroupingProperties)
{
if (node.ChildTransformations != null && node.ChildTransformations.Count > 0)
{
for (int i = 0; i < node.ChildTransformations.Count; i++)
{
Expression e = visitor.TranslateNode(node.ChildTransformations[i].Expression);
expressions.Add(e);
String aliasName = node.Name + "_" + node.ChildTransformations[i].Name;
_aggProperties.Add(CreateEdmProperty(visitor.EdmModel, e.Type, aliasName, true));
}
}
else
{
Expression e = visitor.TranslateNode(node.Expression);
expressions.Add(e);
_aggProperties.Add(CreateEdmProperty(visitor.EdmModel, e.Type, node.Name, true));
}
}
NewExpression newExpression = OeExpressionHelper.CreateTupleExpression(expressions);
LambdaExpression lambda = Expression.Lambda(newExpression, sourceParameter);
MethodInfo groupByMethodInfo = OeMethodInfoHelper.GetGroupByMethodInfo(sourceType, newExpression.Type);
MethodCallExpression groupByCall = Expression.Call(groupByMethodInfo, source, lambda);
var aggTransformation = (AggregateTransformationNode)transformation.ChildTransformations;
if (aggTransformation == null)
{
expressions.Clear();
sourceType = OeExpressionHelper.GetCollectionItemType(groupByCall.Type);
sourceParameter = Expression.Parameter(sourceType);
expressions.Add(Expression.Property(sourceParameter, nameof(IGrouping <Object, Object> .Key)));
newExpression = OeExpressionHelper.CreateTupleExpression(expressions);
MethodInfo selectMethodInfo = OeMethodInfoHelper.GetSelectMethodInfo(sourceType, newExpression.Type);
lambda = Expression.Lambda(newExpression, sourceParameter);
return(Expression.Call(selectMethodInfo, groupByCall, lambda));
}
return(ApplyAggregate(groupByCall, aggTransformation));
}