c# - Best way to remove multiple items matching a predicate from a .NET Dictionary?

Question

I need to remove multiple items from a Dictionary. A simple way to do that is as follows :

  List<string> keystoremove= new List<string>();
  foreach (KeyValuePair<string,object> k in MyCollection)
     if (k.Value.Member==foo)
        keystoremove.Add(k.Key);
  foreach (string s in keystoremove)
        MyCollection.Remove(s);

The reason why I can't directly Remove the items in the foreach block is that this would throw an Exception ("Collection was modified...")

I'd like to do the following :

 MyCollection.RemoveAll(x =>x.Member==foo)

But the Dictionary<> class doesn't expose a RemoveAll(Predicate<> Match) method, like the List<> Class does.

What's the best way (both performance wise and elegant wise) to do that?

Answer 1

Here's an alternate way

foreach ( var s in MyCollection.Where(kv => kv.Value.Member == foo).ToList() ) {
  MyCollection.Remove(s.Key);
}

Pushing the code into a list directly allows you to avoid the "removing while enumerating" problem. The .ToList() will force the enumeration before the foreach really starts.