Threadsafe and generic arraylist in c #?

Question

Hello community,

I want to have a generic thread safe collection and I saw that the Arraylist can easily be used thread safe by its static Synchronized method but what bugs me is that this ArrayList is not generic so when I want to use my objects I always have to cast them. Is there an easier way to do this? Also other list types would be possible.

Thanks in advance

Answer 1

If you read on MSDN regarding the synchronized method is still says this:

"Enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads."

Answer 2

You could create a List(T) wrapper and synchronize access with the SyncRoot property.

MSDN example:

ICollection ic = ...;
lock (ic.SyncRoot) 
{
    // Access the collection.
}

Answer 3

A little knowledge is a dangerous thing ;-) Yes, you could use Meta-Knight's suggestion and use SyncRoot, but you need to be careful - it's not a panacea. See this post from the BCL Team Blog from Microsoft to see why it's not as simple as SyncRoot. Quotes from that post:

A few astute users of our generic collections observed that we no longer provide a public SyncRoot property on ICollection<T>

and

I think we're better off forcing people to think more heavily about synchronization, and frankly a SyncRoot property on our generic collections doesn't provide any value.

Of course, that's not to say it can't be used under any circumstances - you just have to think the use cases through carefully and not be on auto-pilot.