Getting keys from a Lookup

c# .net linq linq-to-objects lookup
magnattic picture magnattic · Apr 26, 2011 · Viewed 15.1k times · Source

How do I get the collection of keys from a Lookup<> I created through the .ToLookup() method?

I have a lookup which maps int-values to groups of instances of a custom class. I need a collection of all the int keys that the lookup contains. Any way to do this, or do I have to collect and save them separately?

Answer

Rup picture Rup · Apr 26, 2011

You can iterate through the set of key-item groups and read off the keys, e.g.

var keys = myLookup.Select(g => g.Key).ToList();

Related questions

How to update an element with a List using LINQ and C#

I have a list of objects and I'd like to update a particular member variable within one of the objects. I understand LINQ is designed for query and not meant to update lists of immutable data. What would be the …

Read More
Conversion from Int array to string array

When I am converting array of integers to array of string, I am doing it in a lengthier way using a for loop, like mentioned in sample code below. Is there a shorthand for this? The existing question and answers …

Read More
Count values in Dictionary using LINQ and LINQ extensions

I have a dictionary that looks something like this: Dictionary<String, List<String>> test1 : 1,3,4,5 test2 : 2,3,6,7 test3 : 2,8 How can I get a count of all the values using LINQ and LINQ extensions?

Read More