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

class SimpleClass
{
   // Static constructor
   static SimpleClass()
   {
       //...
   }
}

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.

Example

In this example, the class Bus has a static constructor and one static member, Drive(). When Drive() is called, the static constructor is invoked to initialize the class.

C#

public class Bus
{
   // Static constructor:
   static Bus()
   {
       System.Console.WriteLine("The static constructor invoked.");
   }

   public static void Drive()
   {
       System.Console.WriteLine("The Drive method invoked.");
   }
}

class TestBus
{
   static void Main()
   {
       Bus.Drive();
   }
}

Output

The static constructor invoked.

The Drive method invoked.