Question

I am trying to combine two SortedDictionaries, change the result to a List<KeyvaluePair<string,string>> and Sort() the result. The following statement throws an error:

var combinedEntries = from p in leftDict.Union(rightDict).ToList().Sort(myComparer) select p;

Error: Could not find an implementation of the query pattern for source type ‘void’. ‘Select’ not found.

This is not working because Sort() returns void. If I split up the statement, it works:

var combinedEntries = from p in leftDict.Union(rightDict) select p;
List<KeyValuePair<string, string>> finalentries = combinedEntries.ToList();
finalentries.Sort(comparer);

I understand that sort is a method of List type and not IEnumerable, but I thought calling ToList() before Sort() will take care of that problem. So first question is can it be used like I am trying in the first statement? If not, how do I make use of orderby here?

Answer 1

You can do combinedEntries = <query goes here>.OrderBy(a => a, myComparer).ToList();.
However, seperately converting it into a list, and explicitly sorting is much more readable, and I’m willing to bet some good money that List.Sort beats OrderBy in performance easily.