Are static delegates thread-safe?

Question

Consider this code snippet:

public static class ApplicationContext
{
    private static Func<TService> Uninitialized<TService>()
    {
        throw new InvalidOperationException();
    }

    public static Func<IAuthenticationProvider> AuthenticationProvider = Uninitialized<IAuthenticationProvider>();
    public static Func<IUnitOfWorkFactory> UnitOfWorkFactory = Uninitialized<IUnitOfWorkFactory>();
}

//can also be in global.asax if used in a web app.
public static void Main(string[] args) 
{
    ApplicationContext.AuthenticationProvider = () => new LdapAuthenticationProvider();
    ApplicationContext.UnitOfWorkFactory = () => new EFUnitOfWorkFactory();
}

//somewhere in the code.. say an ASP.NET MVC controller
ApplicationContext.AuthenticationProvider().SignIn(username, true);

Are delegates in the static class ApplicationContext thread-safe in the sense that multiple-threads can invoke them?

What potential problems will I face if I pursue this approach?

Answer 1

Are delegates in the static class ApplicationContext thread-safe in the sense that multiple-threads can invoke them?

Yes. But a delegate is only as thread-safe as the method it points to.

So, if the methods called by your AuthenticationProvider and UnitOfWorkFactory delegates are thread-safe, then so will your delegates be.

In the code you've provided, these are simply constructor calls. It doesn't really get much more thread-safe than that (unless you've got some crazy threading logic in your constructors -- I certainly hope not).

What potential problems will I face if I pursue this approach?

None that result directly from invoking your delegates. Again, the only concerns regarding thread-safety that you should be worried about are those that pertain to the actual methods called by your delegates (in this case, the constructors for LdapAuthenticationProvider and EFUnitOfWorkFactory).

UPDATE: limpalex made a good observation: in the code you've posted, you are actually calling the Uninitialized<TService> method in the static constructor for your ApplicationContext class, which will throw an exception. What you want to do is assign your delegates to the method. I think what you're going for is something like this:

// note: changed return type to TService to match Func<TService> signature
private static TService Uninitialized<TService>()
{
    throw new InvalidOperationException();
}

// note: removed () symbols to perform assignment instead of method call
public static Func<IAuthenticationProvider> AuthenticationProvider = Uninitialized<IAuthenticationProvider>;
public static Func<IUnitOfWorkFactory> UnitOfWorkFactory = Uninitialized<IUnitOfWorkFactory>;