public static void IfDemo(){
    int i = 0;

    /*  Illegal:  Cannot implicitly convert type 'int' to 'bool'
    if (i){
      Console.WriteLine("i is 0");
    }
    else {
      Console.WriteLine("i is not 0");
    }    
    */

    /* The type of the expression i==0 is boolean  */
    if (i == 0){
      Console.WriteLine("i is 0");
    }
    else {
      Console.WriteLine("i is not 0");
    }    
  }