How to draw and move shapes using mouse in C#

Question

I'm new to programming in C# and wanted to ask for a little bit of help. I'm currently trying to move a color-filled rectangle that I draw on a Windows Application form with my left mouse button, and I'm trying to drag-and-drop it to another location using my right mouse button. Currently I've managed to draw the rectangle, but the right click is dragging the entire form along.

Here's my code:

public partial class Form1 : Form
{
    private Point MouseDownLocation;

    public Form1()
    {
        InitializeComponent();
        this.DoubleBuffered = true;
    }
    Rectangle rec = new Rectangle(0, 0, 0, 0);

    protected override void OnPaint(PaintEventArgs e)
    {   
        e.Graphics.FillRectangle(Brushes.DeepSkyBlue, rec);
    }


    protected override void OnMouseDown(MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left) 
        {
            rec = new Rectangle(e.X, e.Y, 0, 0);
            Invalidate();

        }
        if (e.Button == MouseButtons.Right)
        {
            MouseDownLocation = e.Location;
        }
    }
    protected override void OnMouseMove(MouseEventArgs e)
    {             

        if (e.Button == MouseButtons.Left)
        {
            rec.Width = e.X - rec.X;
            rec.Height = e.Y - rec.Y;
            Invalidate();
        }

        if (e.Button == MouseButtons.Right)
        {
            this.Left = e.X + this.Left - MouseDownLocation.X;
            this.Top = e.Y + this.Top - MouseDownLocation.Y;

        }
    }

}

I only need to drag-and-drop the rectangles with right mouse button.

EDIT: Thanks to you all i got my answer very fast and here's the code that works:

public partial class Form1 : Form
{
    private Point MouseDownLocation;

    public Form1()
    {
        InitializeComponent();
        this.DoubleBuffered = true;            
    }

    Rectangle rec = new Rectangle(0, 0, 0, 0);

    protected override void OnPaint(PaintEventArgs e)
    {
        e.Graphics.FillRectangle(Brushes.DeepSkyBlue, rec);
        //Generates the shape            
    }

    protected override void OnMouseDown(MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left)
        //can also use this one:
        //if (e.Button == System.Windows.Forms.MouseButtons.Left)
        {
            rec = new Rectangle(e.X, e.Y, 0, 0);
            Invalidate();

        }
        if (e.Button == MouseButtons.Right)
        {
            MouseDownLocation = e.Location;
        }
    }
    protected override void OnMouseMove(MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left)
        {
            rec.Width = e.X - rec.X;
            rec.Height = e.Y - rec.Y;
            this.Invalidate();
        }

        if (e.Button == MouseButtons.Right)
        {
            rec.Location = new Point((e.X - MouseDownLocation.X) + rec.Left, (e.Y - MouseDownLocation.Y) + rec.Top);
            MouseDownLocation = e.Location;
            this.Invalidate();
        }
    }

}

Answer 1

This seems to work

    protected override void OnMouseMove(MouseEventArgs e)
    {


        if (e.Button == MouseButtons.Left)
        {
            rec.Width = e.X - rec.X;
            rec.Height = e.Y - rec.Y;
            this.Invalidate();
        }

        if (e.Button == MouseButtons.Right)
        {
            rec.Location = new Point((e.X-MouseDownLocation.X) + rec.Left, (e.Y-MouseDownLocation.Y) + rec.Top);
            MouseDownLocation = e.Location;
            this.Invalidate();
        }
    }