.NET C# - WinForm border

Question

I have a WinForm without a border (borderless). How can I add a 1px black border to the form?

    public MainForm()
    {
        InitializeComponent();
        this.DoubleBuffered = true;
        Region = System.Drawing.Region.FromHrgn(CreateRoundRectRgn(0, 0, Width - 5, Height - 5, 10, 10)); // adjust these parameters to get the lookyou want.
    }


    [DllImport("Gdi32.dll", EntryPoint = "CreateRoundRectRgn")]
    private static extern IntPtr CreateRoundRectRgn
    (
         int nLeftRect, // x-coordinate of upper-left corner
         int nTopRect, // y-coordinate of upper-left corner
         int nRightRect, // x-coordinate of lower-right corner
         int nBottomRect, // y-coordinate of lower-right corner
         int nWidthEllipse, // height of ellipse
         int nHeightEllipse // width of ellipse
     );

I need a borderless form but I want to add a 1px border.

Answer 1

In the Paint event handler of the form, add this code:

private void Form1_Paint(object sender, PaintEventArgs e)
{
    e.Graphics.DrawRectangle(Pens.Black, new Rectangle(0, 0, Width - 1, Height - 1));
}

Good luck!

Answer 2

You could add a fully docked Panel , and another fully docked Panel as a child control. Set the padding of the outer Panel to 1 and the background color of the outer Panel to black.

Then set the background color of the inner Panel to SystemColors.Control .

Answer 3

If you don't want to paint,

Add 4 panels width or height 2 or 4 and black background colour after dock them in 4 sides differently on top, right, bottom, left respectively

        this.FormBorderStyle = FormBorderStyle.None;

        Panel pnlTop = new Panel() { Height = 4, Dock = DockStyle.Top, BackColor = Color.Green };
        this.Controls.Add(pnlTop);

        Panel pnlRight = new Panel() { Width = 4, Dock = DockStyle.Right, BackColor = Color.Green };
        this.Controls.Add(pnlRight);

        Panel pnlBottom = new Panel() { Height = 4, Dock = DockStyle.Bottom, BackColor = Color.Green };
        this.Controls.Add(pnlBottom);

        Panel pnlLeft = new Panel() { Width = 4, Dock = DockStyle.Left, BackColor = Color.Green };
        this.Controls.Add(pnlLeft);

You can also change their mouse pointer to resize icons also you can resize the form writing some code on mouse events.