internal static IQueryable GetSubGroupsAndCountsQueryable(this IQueryable queryable, string subGroupBy, bool sortGroupBy, ListSortDirection direction)
{
// Create GroupBy
Type queryableElementType = queryable.ElementType;
ParameterExpression[] parameters = new ParameterExpression[] { Expression.Parameter(queryableElementType, "") };
MemberExpression memberExpression = QueryableExtensions.GenerateMemberExpression(parameters[0], subGroupBy);
LambdaExpression groupByLambdaExpression = Expression.Lambda(memberExpression, parameters);
MethodCallExpression groupByMethodExpression =
Expression.Call(
typeof(Queryable), "GroupBy",
new Type[] { queryableElementType, groupByLambdaExpression.Body.Type },
new Expression[] { queryable.Expression, Expression.Quote(groupByLambdaExpression) });
IQueryable groupedResult = queryable.Provider.CreateQuery(groupByMethodExpression);
if (sortGroupBy)
{
groupedResult = groupedResult.OrderByKey(direction == ListSortDirection.Ascending);
}
ParameterExpression[] groupedParameters = new ParameterExpression[] { System.Linq.Expressions.Expression.Parameter(groupedResult.ElementType, "") };
MemberExpression keyMemberExpression = MemberExpression.Property(groupedParameters[0], "Key");
MethodCallExpression countCallExpression = MethodCallExpression.Call(typeof(Enumerable), "Count", new Type[] { queryableElementType }, groupedParameters);
QueryableGroupNameCountPairInfo queryableGroupNameCountPairInfo =
QueryableExtensions.QueryableGroupNameCountPairInfos.GetInfosForType(memberExpression.Type);
Expression[] newExpressionArguments = new Expression[2] {
keyMemberExpression, countCallExpression
};
NewExpression newExpression =
NewExpression.New(
queryableGroupNameCountPairInfo.ConstructorInfo,
newExpressionArguments,
new MemberInfo[] { queryableGroupNameCountPairInfo.KeyPropertyInfo, queryableGroupNameCountPairInfo.CountPropertyInfo });
LambdaExpression finalLambdaExpression = System.Linq.Expressions.Expression.Lambda(newExpression, groupedParameters);
MethodCallExpression finalSelectExpression =
System.Linq.Expressions.Expression.Call(
typeof(Queryable), "Select",
new Type[] { groupedResult.ElementType, finalLambdaExpression.Body.Type },
new System.Linq.Expressions.Expression[] { groupedResult.Expression, System.Linq.Expressions.Expression.Quote(finalLambdaExpression) });
return(groupedResult.Provider.CreateQuery(finalSelectExpression));
}