Question

I want to convert an ArrayList to a List<string> using LINQ. I tried ToList() but that approach is not working:

ArrayList resultsObjects = new ArrayList();
List<string> results = resultsObjects.ToList<string>();

Answer 1

Your code actually shows a List<ArrayList> rather than a single ArrayList. If you’re really got just one ArrayList, you’d probably want:

ArrayList resultObjects = ...;
List<string> results = resultObjects.Cast<string>()
                                    .ToList();

The Cast call is required because ArrayList is weakly typed – it only implements IEnumerable, not IEnumerable<T>. Almost all the LINQ operators in LINQ to Objects are based on IEnumerable<T>.

That’s assuming the values within the ArrayList really are strings. If they’re not, you’ll need to give us more information about how you want each item to be converted to a string.