Move rectangle with mouse using translate/transform

Question

I need to make a graph of lines from a csv file and draw it with GDI got a Windows form but now I want to change the scale and move.

I started with something more simple as moving a rectangle with the mouse but to start drawing the rectangle always from the origin. Can anyone help?

My code is:

public partial class Form1 : Form {
    int origenX;
    int origenY;

    bool transformar = false;


    public Form1() {
        InitializeComponent();
    }

    private void Form1_Paint(object sender, PaintEventArgs e) {
        dibujar(e.Graphics);
    }

    private void Form1_MouseMove(object sender, MouseEventArgs e) {
        int deltaX = e.X - origenX;
        int deltaY = e.Y - origenY;

        if (transformar) {
            System.Drawing.Graphics g = this.CreateGraphics();
            Matrix mAux = new Matrix();
            mAux.Translate(deltaX, deltaY);
            g.Transform = mAux;
            dibujar(g);
            g.Dispose();
        }
        this.Text = "x=" + deltaX.ToString() + ", y=" + deltaY.ToString(); 
    }

    private void Form1_MouseDown(object sender, MouseEventArgs e) {
        transformar = true;
        origenX = e.X;
        origenY = e.Y;
    }

    private void Form1_MouseUp(object sender, MouseEventArgs e) {
        transformar = false;
    }

    private void dibujar(System.Drawing.Graphics g) {
        g.Clear(Color.White);
        g.DrawEllipse(new Pen(Color.Blue, 2), new Rectangle(50, 50, 50, 50));
    }
}

Answer 1

Already solved, thanks anyway, the code was as follows:

public partial class Form2 : Form {
    private float dx=0;
    private float dy=0;
    private float X0=1;
    private float Y0=1;

    private bool trasladar = false;

    public Form2() {
        InitializeComponent();
    }

    private void Form2_Paint(object sender, PaintEventArgs e) {
        e.Graphics.TranslateTransform(dx, dy, MatrixOrder.Append);
        e.Graphics.Clear(Color.White);
        e.Graphics.DrawEllipse(new Pen(Color.Blue), new Rectangle(50, 50, 50, 50));
    }

    private void Form2_MouseDown(object sender, MouseEventArgs e) {
        Cursor = Cursors.SizeAll;
        trasladar = true;
        X0 = e.X;
        Y0 = e.Y;
    }

    private void Form2_MouseUp(object sender, MouseEventArgs e) {
        Cursor = Cursors.Default;
        trasladar = false;
    }

    private void Form2_MouseMove(object sender, MouseEventArgs e) {
        if (trasladar) {
            dx += (e.X - X0);
            dy += (e.Y - Y0);
            X0 = e.X;
            Y0 = e.Y;
            Invalidate();
        }
    }
}

Answer 2

Use this.Invalidate(); when the form should redraw.

It will declare the form as invalid, so it will be forced to redraw. Only then the Form1_Paint will be called.

Test this behaivour by doing an Debug output in the Paint-Event. Then you can start further debugging to get what you want.