[assembly: PreApplicationStartMethod(typeof(MyAssembly.Initializer), "Initialize")]

namespace MyAssembly
{
    public static class Initializer
    {
       public static void Initialize()
       {
           TranslationKeys.Initialize();
       }
    }
}

using System;
using System.Web;
using System.Reflection;

public class TestClass {
    public static void TestPreStartInitMethodLocation(Assembly assembly) {
        var attributes = (PreApplicationStartMethodAttribute[])assembly.GetCustomAttributes(typeof(PreApplicationStartMethodAttribute), inherit: true);

        if (attributes != null && attributes.Length != 0) {
            PreApplicationStartMethodAttribute attribute = attributes[0];

            MethodInfo method = null;
            // They must be in the same assembly!
            if (attribute.Type != null && !String.IsNullOrEmpty(attribute.MethodName) && attribute.Type.Assembly == assembly) {
                method = FindPreStartInitMethod(attribute.Type, attribute.MethodName);
            }

            if (method == null) {
                throw new HttpException("Couldn't find attribute");
            }
        }
    }

    public static MethodInfo FindPreStartInitMethod(Type type, string methodName) {
        MethodInfo method = null;
        if (type.IsPublic) {
            method = type.GetMethod(methodName, BindingFlags.Public | BindingFlags.Static | BindingFlags.IgnoreCase,
                            binder: null,
                            types: Type.EmptyTypes,
                            modifiers: null);
        }
        return method;
    }
}