Why are there no concurrent collections in C#?

Question

I am trying to get an overview of the thread safety theory behind the collections in C#.

Why are there no concurrent collections as there are in Java? (java docs). Some

Answer 1

.NET has had relatively "low level" concurrency support until now - but .NET 4.0 introduces the System.Collections.Concurrent namespace which contains various collections which are safe and useful.

Andrew's answer is entirely correct in terms of how to deal with collections before .NET 4.0 of course - and for most uses I'd just lock appropriately when accessing a "normal" shared collection. The concurrent collections, however, make it easy to use a producer/consumer queue, etc.