TypeInitializationException exception on creating an object

Question

I have an assembly (class library project in .Net 3.5) that has some references like System.Configuration and System.Web. I use it on a web application and it works fine.

Now, I need to make a reference to a Windows Forms project and I can't understand what is happening. When I try to create an instance of my class it does not work; an exception of type TypeInitializationException is thrown.

I try to create other instances of my assembly and those work, except this specific class.

Does anybody know what is happening?

Does that class have a static constructor that is throwing an exception? — vcsjones
– vcsjones, Commented Aug 10, 2011 at 20:09

Timothy Fries · Accepted Answer · 2011-08-10 20:11:35Z

73

TypeInitializationException is usually thrown when a static field of the class can't be initialized. For example:

class BadClass
{
    private static MyClass fieldName = new MyClass();
}

Will cause a TypeInitializationException prior to the first usage of BadClass if the constructor for MyClass throws.

You can look at the InnerException property of the TypeInitializationException to drill down into the cause of the failure in more detail. It will usually point you to the underlying exception that caused the type initialization to fail.

answered Aug 10, 2011 at 20:11

Timothy Fries

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4 Comments

driis Over a year ago

It doesn't have to be a field, it can be anything in the static constructor.

Felipe Oriani Over a year ago

Thanks man, I forget it, I was initializing a static field that was looking some configuration ni .config file and now I add this configuration and it works for me. Cheers!

Timothy Fries Over a year ago

@driis: That's true; but I figure by the time you've gotten to the point you're writing a static constructor, you're "advanced" enough that you hopefully understand the consequences of it failing. Whereas simply initializing a static field is something that's common and simple enough that it's a feature that gets used without deeper understanding of the lifecycle of a class, which is why I called it out specifically as a possible cause.

flocbit Over a year ago

Thanks for the hint! I was receiving this issue for half an hour while testing a Xamarin.Android application.

driis · Accepted Answer · 2011-08-10 20:11:24Z

10

TypeInitializationException is thrown when the class initializer fails. There can be a number of reasons to this, but most likely you have some code in your class' static constructor, that throws an exception. You can likely look at the InnerException property to get the real exception.

answered Aug 10, 2011 at 20:11

driis

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Comments

Travis · Accepted Answer · 2016-06-06 21:45:12Z

4

Just to catch another scenario, this error will be thrown when your AppConfig contains a section that is not defined in the configSections node. It's case sensitive, so verify that your custom config sections match what's in the configSections node.

answered Jun 6, 2016 at 21:45

Travis

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2 Comments

Peter Huppertz Over a year ago

Thanks... this might very well have been the answer too -- it was for me!

Oliver Over a year ago

Similarly if the app.config is incorrectly formed XML.

user1412699 · Accepted Answer · 2017-01-17 09:47:33Z

1

For me it was duplicate key in static dictionary

public static Dictionary<string, int> Cities = new Dictionary<string, int>(){
{"New York", 1},
{"Amsterdam", 2},
{"New York", 1}
};

answered Jan 17, 2017 at 9:47

user1412699

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