错误：Daemon.Global的类型初始化器在c＃中引发异常

Question

I am using the below class file, where some variables are declared to use in the entire application. Now I used that variable BlockLogOut in another class file to make the value true.

I just put this below line and getting error in it.. TypeInitializationException

Global.BlockLogOut = True;

The weird thing is, it was working fine for many months and i am getting this error now on the above line. Of course i was modifying some other stuffs in the application, but surely not this class file. What would have been the problem?

Inner Exception : system.null reference exception, object reference not set to an instance of an object

   namespace Daemon
    {
        class Global
        {
            public static bool BlockLogOut = false;
        }
    }

Answer 1

This error TypeInitializationException : The exception that is thrown as a wrapper around the exception thrown by the class initializer. This class cannot be inherited.

Answer 2

I assume the sample code is not the full code in your Global class. A null reference exception indicates that you are using a class instance somewhere in your static constructor; it's not related to the GlobalLock variable you have included in the code since is a value type and not a class.

Answer 3

I bet that you have a static constructor :) If so, then the exception actually occurs inside the static constructor.

namespace Daemon
{
    using System;

    public class Global
    {
        public static bool BlockLogOut = false;

        static Global()
        {
            throw new Exception();
        }
    }
}

namespace ConsoleApplication
{
    public class Program
    {
        static void Main(string[] args)
        {
            Daemon.Global.BlockLogOut = true; // TypeInitializationException
        }
    }
}

Answer 4

Have you changed your target framework to .NET 4.0 recently? Because this may be due to Type initialization changes in .NET 4.0 (Jon Skeet has a post about it on his blog).

Long story short, there has been some changes about how and when a type will be initialized by the CLR. While it still conforms to the specification, it does so in a lazier fashion. Again, in a nutshell, it won't initialize fields until it actually needs them (I'm not too sure about the peculiarities of these changes though).

Make sure you don't depend on BlockLogOut being initialized in some sort of empty Initialize() { } method. It won't actually be initialized until a method that uses it gets called (and yes, that's applicable to constructors and instance methods too; As long as they don't use that particular field).

But as always, you are guarantied that the field will be initialized before you need it and that this initialization will happen at most once.