Using constructor how to do this one

Make the constructor private:

public class MyClass
   {
   private static MyClass theInstance = new MyClass();
   private MyClass() {}
   public static MyClass GetInstance()
      {
      return theInstance;
      }
   }

The app can only create a single instance of the class, because the constructor is only available within the class itself.

This is also known as a Singleton pattern.