How to draw a rectangle in C# using a mouse - c#-3.0

Question

I want to draw a rectangle on a form in C#. I read and found this article. Are there any samples or tutorials available ? The article was not very helpful.

Answer 1

The article you linked appears to be C++, which may explain why it didn't help you much.
If you create events for MouseDown and MouseUp, you should have the two corner points you need for a rectangle. From there, it's a matter of drawing on the form. System.Drawing.* should probably be your first stop. There are a couple of tutorials linked below:
Drawing with Graphics in WinForms using C#
Draw a rectangle using Winforms (StackOverflow)
Graphics Programming using C#

Answer 2

You need this 3 functions and variables:
private Graphics g;
Pen pen = new System.Drawing.Pen(Color.Blue, 2F);
private Rectangle rectangle;
private int posX, posY, width, height;
Second you need to make a mouse down event:
private void pictureCrop_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
posX = e.X;
posY = e.Y;
}
}
Third, you need to implemente the mouse up event:
private void pictureCrop_MouseUp(object sender, MouseEventArgs e)
{
if (e.Button != MouseButtons.Left)
return;
if (e.X > posX && e.Y > posY) // top left to bottom right
{
width = Math.Abs(e.X - posX);
height = Math.Abs(e.Y - posY);
}
else if (e.X < posX && e.Y < posY) // bottom right to top left
{
width = Math.Abs(posX - e.X);
height = Math.Abs(posY - e.Y);
posX = e.X;
posY = e.Y;
}
else if (e.X < posX && e.Y > posY) // top right to bottom left
{
width = Math.Abs(posX - e.X);
height = Math.Abs(posY - e.Y);
posX = e.X;
}
else if (e.X > posX && e.Y < posY) // bottom left to top right
{
width = Math.Abs(posX - e.X);
height = Math.Abs(posY - e.Y);
posY = e.Y;
}
g.DrawImage(_bitmap, 0, 0);
rectangle = new Rectangle(posX, posY, width, height);
g = pictureCrop.CreateGraphics();
g.DrawRectangle(pen, rectangle);
}
And to ensure that when you resize or move the form the rectangle will be there:
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
Graphics graph = e.Graphics;
graph.DrawImage(_bitmap, 0, 0);
Rectangle rec = new Rectangle(posX, posY, width, height);
graph.DrawRectangle(pen, rec);
}