How to Create a Thread-Safe Generic List?

Question

I have a Generic List as below

public static readonly List<Customer> Customers = new List<Customer>(); 

I'm using the below methods for it:

.Add .Find .FirstOrDefault 

The last 2 are LINQ extensions.

I'd need to make this thread-safe to be able to run multiple instances of the container class.

How to achieve that?

Answer 1

If those are the only functions you are using on List<T> then the easiest way is to write a quick wrapper that synchronizes access with a lock

class MyList<T> {    private List<T> _list = new List<T>();   private object _sync = new object();   public void Add(T value) {     lock (_sync) {       _list.Add(value);     }   }   public bool Find(Predicate<T> predicate) {     lock (_sync) {       return _list.Find(predicate);     }   }   public T FirstOrDefault() {     lock (_sync) {       return _list.FirstOrDefault();     }   } } 

I highly recommend the approach of a new type + private lock object. It makes it much more obvious to the next guy who inherits your code what the actual intent was.

Also note that .Net 4.0 introduced a new set of collections specifically aimed at being used from multiple threads. If one of these meets your needs I'd highly recommend using it over rolling your own.

• ConcurrentStack<T>
• ConcurrentQueue<T>