Static

Defining Static Constructors

• A given class may define only a single static constructor. In other words, the static constructor cannot be overloaded
• A static constructor does not take an access modifier and cannot take any parameters
• A static constructor executes exactly one time, regardless of how many objects of the type are created
• The run-time invokes the static constructor when it creates an instance of the class or before accessing the first static member invoked by the caller
• The static constructor executes before any instance-level constructors.

Defining Static Classes

Declaration Static Class

// Static classes can only contain static members!
static class TimeUtilClass
{
  public static void PrintTime()
  { Console.WriteLine(DateTime.Now.ToShortTimeString()); }
 
  public static void PrintDate()
  { Console.WriteLine(DateTime.Today.ToShortDateString()); }
}

Using Static Class

cannot create an instance of TimeUtilClass using the new keyword
static void Main(string[] args)
{
  Console.WriteLine("***** Fun with Static Data *****\n");
 
  // This is just fine.
  TimeUtilClass.PrintDate();
  TimeUtilClass.PrintTime();
  // Compiler error! Can't create static classes!
  TimeUtilClass u = new TimeUtilClass ();
...
}

The only way to prevent the creation of a class that only exposed static functionality was to either redefine the default constructor using the private keyword or mark the class as an abstract type using the C# abstract keyword

Two ways to prevent the creation of a class
class TimeUtilClass2 
{ 
  // Redefine the default ctor as private  to prevent creation. 
   private TimeUtilClass2 (){} ***Way1***
 
  public static void PrintTime() 
  { Console.WriteLine(DateTime.Now.ToShortTimeString()); } 
  public static void PrintDate() 
  { Console.WriteLine(DateTime.Today.ToShortDateString()); }
} 
// Define type as abstract to prevent creation. 
abstract class TimeUtilClass3  ***Way2***
{ 
  public static void PrintTime() 
  { Console.WriteLine(DateTime.Now.ToShortTimeString()); } 
  public static void PrintDate() 
  { Console.WriteLine(DateTime.Today.ToShortDateString()); } 
}