//  SumApplication.cs  Copyright (c) Kari Laitinen

//  http://www.naturalprogramming.com

//  2008-02-25  File created.
//  2022-12-20  Tested in Developer Command Prompt for VS 2022.

/*  With this program you can calculate the sum of two integers.
    This program demonstrates the following things:
      - the use of Panel, TextBox, and Label objects

    In Windows terminology, the various GUI components (e.g.
    TextBox, Label, Panel) are called controls.

    More notes at the end of this file.
*/

using System ;
using System.Windows.Forms ;
using System.Drawing ;

class SumForm : Form
{
   const int WINDOW_WIDTH  =  600 ;
   const int WINDOW_HEIGHT =  435 ;

   TextBox first_text_box, second_text_box ;
   Label   result_label ;

   public SumForm()
   {
      Text = "CALCULATE THE SUM OF TWO INTEGERS" ;
      Size = new Size( WINDOW_WIDTH, WINDOW_HEIGHT ) ;

      //  First we specify a Panel into which we will later attach
      //  Label and TextBox objects.

      Panel  calculation_panel  =  new Panel() ;

      //  The following statement specifies that the position
      //  of the panel is ( 100, 50 ), and its width is 300 pixels
      //  and its height is 150 pixels.

      calculation_panel.Bounds = new Rectangle( 100, 50, 300, 150 ) ;

      //  Next, we'll create Label and TextBox objects.
      //  The Bounds property of these objects will be set so
      //  that they fit nicely into the "calculation panel"
      //  that was created earlier.

      Label first_integer_label  = new Label() ;
      first_integer_label.Text = "First integer:" ;
      first_integer_label.Bounds = new Rectangle(  0,   0, 150, 50 ) ;

      Label second_integer_label = new Label() ;
      second_integer_label.Text = "Second integer:" ;
      second_integer_label.Bounds = new Rectangle( 0,  50, 150, 50 ) ;

      Label calculated_sum_label = new Label() ;
      calculated_sum_label.Text = "Calculated sum:" ;
      calculated_sum_label.Bounds = new Rectangle( 0, 100, 150, 50 ) ;

      Font font_for_numbers  =  new  Font( FontFamily.GenericMonospace,
                                           14, FontStyle.Bold ) ;

      first_text_box  =  new  TextBox() ;
      first_text_box.TextAlign = HorizontalAlignment.Right ;
      first_text_box.Font = font_for_numbers ;
      first_text_box.Bounds =  new Rectangle( 150,  0, 150, 50 ) ;
      first_text_box.TextChanged +=
                         new EventHandler( text_box_text_changed ) ;

      second_text_box  =  new  TextBox() ;
      second_text_box.TextAlign = HorizontalAlignment.Right ;
      second_text_box.Font = font_for_numbers ;
      second_text_box.Bounds = new Rectangle( 150, 50, 150, 50 ) ;
      second_text_box.TextChanged +=
                         new EventHandler( text_box_text_changed ) ;

      result_label  =  new  Label() ;
      result_label.TextAlign = ContentAlignment.TopRight ;
      result_label.Font = font_for_numbers ;
      result_label.Bounds = new Rectangle( 150, 100, 150, 50 ) ;
      result_label.Text = "0" ;

      //  Next, we'll add the GUI components (or controls) to the panel

      calculation_panel.Controls.Add( first_integer_label ) ;
      calculation_panel.Controls.Add( second_integer_label ) ;
      calculation_panel.Controls.Add( calculated_sum_label ) ;

      calculation_panel.Controls.Add( first_text_box ) ;
      calculation_panel.Controls.Add( second_text_box ) ;
      calculation_panel.Controls.Add( result_label ) ;

      Controls.Add( calculation_panel ) ; // Add the panel to the form
   }

   private void text_box_text_changed( object    sender,
                                       EventArgs event_data )
   {
      String first_text  = first_text_box.Text ;
      String second_text = second_text_box.Text ;

      //  The following two if constructs ensure that empty text boxes
      //  are treated as if they contained a zero.

      if ( first_text.Length == 0 )
      {
         first_text  =  "0" ;
      }

      if ( second_text.Length == 0 )
      {
         second_text = "0" ;
      }

      try
      {
         int first_integer  = Convert.ToInt32( first_text ) ;
         int second_integer = Convert.ToInt32( second_text ) ;
         int sum_of_two_integers  =  first_integer  +  second_integer ;
         result_label.Text = "" + sum_of_two_integers ;
      }
      catch ( Exception )
      {
         result_label.Text = "INPUT ERROR!" ;
      }
   }
}

public class SumApplication
{
   static void Main()
   {
      Application.Run( new SumForm() ) ;
   }
}

/* POSSIBLE EXERCISE:

   Modify the program so that you can write negative
   numbers to the text boxes. If you now enter a minus
   sign, the program says "INPUT ERROR!". (You can,
   though, currently enter negative numbers if you
   first type a positive number, and then add the
   minus sign.)




*/