A static constructor is used to initialize any static data,
or to perform a particular action that needs to be performed once only. It is called automatically before the first instance is created or any static members are referenced.

Static constructors have the following properties:

• A static constructor does not take access modifiers or have parameters.

• A static constructor is called automatically to initialize the class before the first instance is created or any static members
  are referenced.

• A static constructor cannot be called directly.

• The user has no control on when the static constructor is executed in the program.

• A typical use of static constructors is when the class is using a log file and the constructor is used to write entries to this file.

• Static constructors are also useful when creating wrapper classes for unmanaged code, when the constructor can call the LoadLibrary method.

• If a static constructor throws an exception, the runtime will not invoke it a second time, and the type will remain uninitialized for the lifetime of the application domain in which your program is running.

Example:

   class Student

   {

      public Student()

      {

         Console.WriteLine("Instance constructor");

      }

      static Student()

      {

         Console.WriteLine("Static constructor");

      }

   }

Student stu = new Student();

output:

Static constructor

Instance constructor