How can I run a static constructor?

Question

I\'d like to execute the static constructor of a class (i.e. I want to \"load\" the class) without creating an instance. How do I do that?

Bonus question: Are there

Answer 1

Just reference one of your static fields. This will force your static initialization code to run. For example:

public class MyClass
{
    private static readonly int someStaticField;

    static MyClass() => someStaticField = 1;

    // any no-op method call accepting your object will do fine
    public static void TouchMe() => GC.KeepAlive(someStaticField);
}

Usage:

// initialize statics
MyClass.TouchMe();

Answer 2

I'm not exactly sure what your use case is for this, but you can force static initializers to run in a fairly hacky way using partial classes and inner classes:

The idea is to use a partial outter class with a static field that accesses another static field on the inner class. When the outter class is statically initialized, the static field initialization will kick-off the static initialization of all the inner classes:

public partial class OutterClass
{
    // When OutterClass is initialized, this will force InnerClass1 to be initialized.
    private static int _innerClass1Touched = InnerClass1.TouchMe;

    public static class InnerClass1
    {
        public static int TouchMe = 0;

        static InnerClass1()
        {
            Console.WriteLine("InnerClassInitialized");
        }
    }
}

public partial class OutterClass
{
    // When OutterClass is initialized, this will force InnerClass2 to be initialized.
    private static int _innerClass2Touched = InnerClass2.TouchMe;

    public static class InnerClass2
    {
        public static int TouchMe = 0;

        static InnerClass2()
        {
            Console.WriteLine("InnerClass2Initialized");
        }
    }
}

Then, somewhere early in your application, you just need to reference OutterClass in a way that will result in static initialization, like constructing an instance of it.

A more realistic example might be...

public interface IService
{
    void SayHello();
}

public partial class ServiceRegistry
{
    private static List<Func<IService>> _serviceFactories;

    private static void RegisterServiceFactory(Func<IService> serviceFactory)
    {
        // This has to be lazily initialized, because the order of static initialization
        //  isn't defined. RegisterServiceFactory could be called before _serviceFactories
        //  is initialized.
        if (_serviceFactories == null)
            _serviceFactories = new List<Func<IService>>();

        _serviceFactories.Add(serviceFactory);
    }

    public List<IService> Services { get; private set; }

    public ServiceRegistry()
    {
        Services = new List<IService>();

        foreach (var serviceFactory in _serviceFactories)
        {
            Services.Add(serviceFactory());
        }
    }
}


// In another file (ServiceOne.cs):
public class ServiceOne : IService
{
    void IService.SayHello()
    {
        Console.WriteLine("Hello from ServiceOne");
    }
}

public partial class ServiceRegistry
{
    // When OutterClass is initialized, this will force InnerClass1 to be initialized.
    private static int _serviceOneRegistryInitializer = ServiceOneRegistry.Initialize;

    private static class ServiceOneRegistry
    {
        public static int Initialize = 0;

        static ServiceOneRegistry()
        {
            ServiceRegistry.RegisterServiceFactory(() => new ServiceOne());
        }
    }
}

// In another file (ServiceTwo.cs):
public class ServiceTwo : IService
{
    void IService.SayHello()
    {
        Console.WriteLine("Hello from ServiceTwo");
    }
}

public partial class ServiceRegistry
{
    // When OutterClass is initialized, this will force InnerClass1 to be initialized.
    private static int _serviceTwoRegistryInitializer = ServiceTwoRegistry.Initialize;

    private static class ServiceTwoRegistry
    {
        public static int Initialize = 0;

        static ServiceTwoRegistry()
        {
            ServiceRegistry.RegisterServiceFactory(() => new ServiceTwo());
        }
    }
}

static void Main(string[] args)
{
    ServiceRegistry registry = new ServiceRegistry();
    foreach (var service in registry.Services)
    {
        serivce.SayHello();
    }

    // Output will be:
    // Hello from ServiceOne
    // Hello from ServiceTwo

    // No guarantee on order.
}

Why even do this? It has a very narrow use-case. It eliminates the need to have a single method that initializes and registers all the services. The case in which I personally want to eliminate that single method initialization is for code generation purposes.

Answer 3

As others have said, static constructors run automatically. If you need to be explicit, maybe you should refactor it into a static method which you can run explicitly?

Explicitly calling a static method would also, of course, ensure that the static constructor had been executed.

edit

Static constructors are run when any static members are referenced. You could simply create a dummy method called initialize which did nothing but ensure that the framework calls the static constructor.

Answer 4

Also you can do this:

type.TypeInitializer.Invoke(null, null);