Question

I have a list of Dictionaries.

List<Dictionary<String, String>> data = GetData();

The dictionaries contain a key named “Month” with values like “1/2010” etc. I need a list of strings with all different months that appear in the Dictionary-list.

Answer 1

Simple with LINQ:

var months = data.Select(dict => dict["Month"]).Distinct().ToList();

Or if not all of the dictionaries had the entry:

var months = data.Select(dict => {
                            string value;
                            bool hasValue = dict.TryGetValue("Month", out value);
                            return new { value, hasValue };
                         })
                 .Where(p => p.hasValue)
                 .Select(p => p.value)
                 .Distinct()
                 .ToList();

EDIT: My original version didn’t include the Distinct call, so it would have included duplicates. It now won’t.