What’s wrong with this code? The following code should draw a BlueViolet circle of diameter 4 that corresponds to the movement of the mouse. Find the error(s) in the following code:
private void FrmPainter_MouseMove(
object sender, System.Windows.Forms.MouseEventArgs e )
{
if ( m_blnshouldPaint == true )
{
Graphics objGraphic = Graphics();
objGraphic.FillEllipse = (
new SolidBrush( Color.BlueViolet ), e.Y, e.X, 5, 4 );
}
} // end method FrmPainter_MouseMove
The position arguments in the FillEllipse method have been transposed. Use
method CreateGraphics to initialize a Graphics object. A circle’s height and width must be equal, so the fourth argument passed to method FillEllipse should be 4. There should be no assignment operator between the word FillEllipse and the parenthesis. The complete incorrect code reads:
// Painter.cs (Incorrect)
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
namespace Painter
{
///
/// Summary description for FrmPainter.
///
public class FrmPainter : System.Windows.Forms.Form
{
///
/// Required designer variable.
///
private System.ComponentModel.Container components = null;
private bool m_blnShouldPaint = true;
public FrmPainter()
{
//
// Required for Windows Form Designer support
//
InitializeComponent();
//
// TODO: Add any constructor code after InitializeComponent
// call
//
}
///
/// Clean up any resources being used.
///
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
// Windows Form Designer generated code
///
/// The main entry point for the application.
///
[STAThread]
static void Main()
{
Application.Run(new FrmPainter());
}
// draws a violet ellipse wherever the mouse moves
private void FrmPainter_MouseMove(
object sender, System.Windows.Forms.MouseEventArgs e )
{
if ( m_blnshouldPaint == true )
{
Graphics objGraphic = Graphics();
objGraphic.FillEllipse = (
new SolidBrush( Color.BlueViolet ), e.Y, e.X, 5, 4 );
}
} // end method FrmPainter_MouseMove
} // end class FrmPainter
}
The complete corrected code should read:
// Painter.cs (Correct)
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
namespace Painter
{
///
/// Summary description for FrmPainter.
///
public class FrmPainter : System.Windows.Forms.Form
{
///
/// Required designer variable.
///
private System.ComponentModel.Container components = null;
private bool m_blnShouldPaint = true;
public FrmPainter()
{
//
// Required for Windows Form Designer support
//
InitializeComponent();
//
// TODO: Add any constructor code after InitializeComponent
// call
//
}
///
/// Clean up any resources being used.
///
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
// Windows Form Designer generated code
///
/// The main entry point for the application.
///
[STAThread]
static void Main()
{
Application.Run( new FrmPainter() );
}
// draws a violet ellipse wherever the mouse moves
private void FrmPainter_MouseMove(
object sender, System.Windows.Forms.MouseEventArgs e )
{
if ( m_blnshouldPaint == true )
{
Graphics objGraphic = CreateGraphics();
objGraphic.FillEllipse(
new SolidBrush( Color.BlueViolet ), e.X, e.Y, 4, 4 );
}
} // end method FrmPainter_MouseMove
} // end class FrmPainter
}
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