Greetings Bill.
In order to understand what's going on, you first need to have a grasp of how constructors usually work, and also of what the word "static" means. So here's a very simple back-to-basics tutorial. I apologise if it's telling you what you already know.
A constructor is called when an instance of a class is created. Its purpose is to perform initialisation of that instance. Here's an example.
// A class with a constructor.
public class MyClass
{
// Some data for the class.
public int Number{get; set;}
// A constructor.
public MyClass()
{
Number = 4;
}
}
// Some code from somewhere in the rest of the program
// Create an instance of MyClass.
MyClass mc1 = new MyClass();
// At this point mc1.Number will be 4.
// Now change it to something else.
mc1.Number = 5;
Create another instance of the class.
MyClass mc2 = new MyClass();
// At this point mc2.Number is 4, but mc1.Number is 5.
So the constructor for MyClass is called every time we create a new instance of the class. It is not called every time we access any of the data in a class instance. When it is called, it acts on that instance alone.
If you can get a handle on that, the next thing to understand is that the word "static" essentially means "there's only one of this". That is, if it's applied to a class, there cannot be multiple instances of that class, and in fact the class cannot be instantiated
at all (you can't use the "new" keyword to create it). A static class just exists as a single entity.
Now, if we put these two concepts together and come up with a "static constructor", it should be clear that we get a constructor that is used to initialise something that exists only as a single entity, so it gets executed only once. You can test this by
putting a Console.WriteLine into the constructor and you will see the line being written just once.
Looking at your third question, this approach of using a static class to hold "global" data is perfectly legit. There are other ways around this problem, and object oriented fundamentalists will probably tell you that they are better ways, but if a static
class works for you then go for it.
As for the second question, I can't explain that error. Unless the classes in question are in a separate file which is missing the "using System" declaration at the top.
