ascending/descending in LINQ - can one change the order via parameter?

Question

I have a method which is given the parameter "bool sortAscending". Now I want to use LINQ to create sorted list depending on this parameter. I got then this:

var ascendingQuery = from data in dataList                       orderby data.Property ascending                       select data;  var descendingQuery = from data in dataList                       orderby data.Property descending                       select data; 

As you can see, both queries differ only in "ascending" resp. "descending". I'd like to merge both queries, but I don't know how. Does anyone have the answer?

Answer 1

You can easily create your own extension method on IEnumerable or IQueryable:

public static IOrderedEnumerable<TSource> OrderByWithDirection<TSource,TKey>     (this IEnumerable<TSource> source,      Func<TSource, TKey> keySelector,      bool descending) {     return descending ? source.OrderByDescending(keySelector)                       : source.OrderBy(keySelector); }  public static IOrderedQueryable<TSource> OrderByWithDirection<TSource,TKey>     (this IQueryable<TSource> source,      Expression<Func<TSource, TKey>> keySelector,      bool descending) {     return descending ? source.OrderByDescending(keySelector)                       : source.OrderBy(keySelector); } 

Yes, you lose the ability to use a query expression here - but frankly I don't think you're actually benefiting from a query expression anyway in this case. Query expressions are great for complex things, but if you're only doing a single operation it's simpler to just put that one operation:

var query = dataList.OrderByWithDirection(x => x.Property, direction);