Question

I am developing a very rudimentary drawing program: A 2D grid comprised of multiple RectangleShapes, around 20×30 pixels each, which when clicked change color based on user RGB input, which works just fine:

Color SelectedColor = new Color();
private void Pixel_1_1_Click(object sender, EventArgs e)    // on Rectangle click
{
    Pixel_1_1.FillColor = SelectedColor;    // change to currently desired color.
}

Since the number of squares is rising dramatically, I’m looking for a way to arrange the “pixel” rectangles into a 2D array. (I really don’t want to have to make a Pixel_Click method for every single Rectangle on the screen!) Hoping eventually to be able to call something like:

private void Pixel_[x]_[y]_Click(object sender, EventArgs e)
{
    Pixel_[x]_[y].FillColor = SelectedColor;
}

My friends suggest the use of an anonymous delegate, but I don’t understand how to fully use one to solve my problem.

What would be the best way to generate a 2D array of rectangles in a C# Windows Form? And once generated, how can I access them with a single method for variant values of x and y?

Answer 1

While you are probably correct in thinking of each rectangle as an object, it probably isn’t correct to think of each rectangle as a windows control, especially since you have so many of them.

So try creating your own rectangle object:

public class MyRect {
  public Color FillColor { get; set; }
  public Rectangle Rectangle { get; set; }

  public MyRect(Rectangle r, Color c) {
    this.Rectangle = r;
    this.FillColor = c;
  }
}

Now you just need to keep a list of your objects and paint on a single Panel control (or PictureBox) all of your rectangles:

private List<MyRect> myRectangles = new List<MyRect>();

public Form1() {
  InitializeComponent();

  myRectangles.Add(new MyRect(new Rectangle(10, 10, 64, 16), Color.Blue));
  myRectangles.Add(new MyRect(new Rectangle(20, 48, 16, 64), Color.Red));
}

private void panel1_Paint(object sender, PaintEventArgs e) {
  foreach (MyRect mr in myRectangles) {
    using (SolidBrush sb = new SolidBrush(mr.FillColor)) {
      e.Graphics.FillRectangle(sb, mr.Rectangle);
    }
  }
}

To handle the “click” event of the rectangles, you just handle the MouseDown or MouseClick event of your container control and determine yourself which rectangle is being clicked on:

void panel1_MouseDown(object sender, MouseEventArgs e) {
  if (e.Button == MouseButtons.Left) {
    foreach (MyRect mr in myRectangles) {
      if (mr.Rectangle.Contains(e.Location)) {
        ChangeColor(mr, Color.Green);
      }
    }
    panel1.Invalidate();
  }
}

private void ChangeColor(MyRect mr, Color newColor) {
  mr.FillColor = newColor;
}