Answer by Zar Shardan for LINQ equivalent of foreach for IEnumerable

This "functional approach" abstraction leaks big time. Nothing on the language level prevents side effects. As long as you can make it call your lambda/delegate for every element in the container - you will get the "ForEach" behavior.

Here for example one way of merging srcDictionary into destDictionary (if key already exists - overwrites)

this is a hack, and should not be used in any production code.

var b = srcDictionary.Select(
                             x=>
                                {
                                  destDictionary[x.Key] = x.Value;
                                  return true;
                                }
                             ).Count();