recently began to study C #, and I can not do this task: create a program that allows you to draw graphic format primitive: circle, segment, rectangle, sector, text, ellipse, and the painted sector. The selection of this or that graphic primitive is carried out using the ListBox control. I would be grateful for the help.

Answer 1

only for seed …

Let’s start with abstraction

public enum figuretype
{
  Circle,
  Line
  Rectangle
  Sector
  Text
  Ellipse,
  Shadedsector
}
Interface IFigure.
{
  FigureType Type {Get; }
  STRING NAME {GET; }
  Point FirstPoint {Get; SET; }
  Point SecondPoint {Get; SET; }
}

Next, implement the interface so

class figure: ifigure
{
  // Ctor.
  Public Figure (FigureType FigureType, String Name)
  {
    if (String.ISNULLOREMPTY (Name)) Throw New ArgumentException (Nameof (Name));
    Type = FigureType;
    Name = Name;
  }
  Public FigureType Type {Get; Private SET; }
  Public String Name {Get; Private SET; }
  Public Point FirstPoint {Get; SET; }
  Public Point SecondPoint {Get; SET; }
}

The form itself is such a

Public Partial Class Form1: Form
{
  Private iFigure _selectedfigure;
  Private Bool _isdrawing;
  Public Form1 ()
  {
    Initializecomponent ();
    SETDATATOLISTBOX ();
    _ListBoxFigures.SelectedIndExchanged + = listboxfigures_selectedchanged;
    _panelcanvas.mousedown + = panelcanvas_mousedown;
    _panelcanvas.mouseup + = panelcanvas_mouseup;
    _panelcanvas.paint + = panelcanvas_paint;
    this.centerToScreen ();
    this.text = "facing";
  }
  /// & LT; Summary & GT;
  /// Filling a list
  /// & LT; / Summary & GT;
  Private Void SetDatatolistBox ()
  {
    _ListBoxFigures.Datasource = New List & LT; ifigure & gt;
    {
      New Figure (FigureType.line, "Cut"),
      New Figure (FigureType.Rectangle, "Rectangle"),
      New Figure (FigureType.circle, "Circle"),
    };
    _ListBoxFigures.displayMember = NameOF (ifigure.name);
  }
  /// & LT; Summary & GT;
  /// Processing Event Selection in the list
  /// & LT; / Summary & GT;
  /// & LT; Param Name = "Sender" & gt; & lt; / param & gt;
  /// & LT; Param name = "E" & gt; & lt; / param & gt;
  Private Void ListBoxFigures_SelectedChanged (Object Sender, Eventargs E)
  {
    if (_listboxfigures.selecteditem == null) return;
    _SelectedFigure = _ListBoxFigures.SelectedItem as ifigure;
  }
  /// & LT; Summary & GT;
  /// Processing Event Pressing the left mouse button on the panel
  /// & LT; / Summary & GT;
  /// & LT; Param Name = "Sender" & gt; & lt; / param & gt;
  /// & LT; Param name = "E" & gt; & lt; / param & gt;
  Private Void Panelcanvas_mouseDown (Object Sender, MouseEventArgs E)
  {
    if (_selectedfigure == NULL) RETURN;
    _selectedfigure.firstPoint = New Point (E.X, E.Y);
  }
  /// & LT; Summary & GT;
  /// Processing Event Release Mouse Button On Panel
  /// & LT; / Summary & GT;
  /// & LT; Param Name = "Sender" & gt; & lt; / param & gt;
  /// & LT; Param name = "E" & gt; & lt; / param & gt;
  Private Void Panelcanvas_mouseup (Object Sender, MouseEventArgs E)
  {
    if (_selectedfigure == NULL) RETURN;
    _selectedfigure.secondpoint = new point (E.X, E.Y);
    _ISDRAWING = TRUE;
    _panelcanvas.refresh ();
  }
  /// & LT; Summary & GT;
  /// Processing Event Perverted Panel
  /// & LT; / Summary & GT;
  /// & LT; Param Name = "Sender" & gt; & lt; / param & gt;
  /// & LT; Param name = "E" & gt; & lt; / param & gt;
  Private Void PanelcanVas_Paint (Object Sender, Painteventargs E)
  {
    if (! _isdrawing) Return;
    Switch (_selectedfigure.Type)
    {
      Case figuretype.circle:
        Throw New NotimplementeDextException ();
      Case FigureType.Line:
        Drawline (E.Graphics);
        Break;
      Case FigureType.Rectangle: 
DrawRectangle (E.Graphics);
        Break;
      Case FigureType.Sector:
        Throw New NotimplementeDextException ();
      Case FigureType.Text:
        Throw New NotimplementeDextException ();
      Case FigureType.ellipse:
        Throw New NotimplementeDextException ();
      Case FigureType.ShadedSector:
        Throw New NotimplementeDextException ();
    }
    _Isdrawing = false;
  }
  /// & LT; Summary & GT;
  /// Drawing a rectangle
  /// & LT; / Summary & GT;
  /// & lt; Param name = "Graphics" & gt; & lt; / param & gt;
  PRIVATE VOID DrawRectangle (Graphics Graphics)
  {
    var width = _selectedfigure.secondpoint.x - _selectedfigure.firstpoint.x;
    var height = _selectedfigure.secondpoint.y - _selectedfigure.firstpoint.y;
    VAR Rectangle =.
      new rectangle (_selectedfigure.firstpoint.x, _selectedfigure.firstpoint.y, width, height);
    Pen Blackpen = New Pen (Color.Black, 5);
    Graphics.DRAWRectangle (Blackpen, Rectangle);
    blackpen.dispose ();
  }
  /// & LT; Summary & GT;
  /// Drawing line
  /// & LT; / Summary & GT;
  /// & lt; Param name = "Graphics" & gt; & lt; / param & gt;
  Private Void Drawline (Graphics Graphics)
  {
    Pen Blackpen = New Pen (Color.Black, 5);
    graphics.drawline (BlackPen, _selectedfigure.firstpoint, _selectedfigure.secondpoint);
    blackpen.dispose ();
  }
}

works it so

Whole example can be downloaded here