How to draw a rounded rectangle in c#

Question

I am using this code to make a rounded rectangle, but it only draws upper left and right corners of rectangle, more it doesn't not complete the rectangle at lower part. How do I make it complete and filled. What changes should I make?

public static Bitmap DrawRoundedRectangle(Bitmap Image, Color BoxColor, int XPosition, int YPosition,
        int Height, int Width, int CornerRadius)

{
    Bitmap NewBitmap = new Bitmap(Image, Image.Width, Image.Height);
    using (Graphics NewGraphics = Graphics.FromImage(NewBitmap))
    {
        using (Pen BoxPen = new Pen(BoxColor))
        {
            using (GraphicsPath Path = new GraphicsPath())
            {
                Path.AddLine(XPosition + CornerRadius, YPosition, XPosition + Width - (CornerRadius * 2), YPosition);
                Path.AddArc(XPosition + Width - (CornerRadius * 2), YPosition, CornerRadius * 2, CornerRadius * 2, 270, 90);
                Path.AddLine(XPosition + Width, YPosition + CornerRadius, XPosition + Width, YPosition + Height - (CornerRadius * 2));
                Path.AddArc(XPosition + Width - (CornerRadius * 2), YPosition + Height - (CornerRadius * 2), CornerRadius * 2, CornerRadius * 2, 0, 90);
                Path.AddLine(XPosition + Width - (CornerRadius * 2), YPosition + Height, XPosition + CornerRadius, YPosition + Height);
                Path.AddArc(XPosition, YPosition + Height - (CornerRadius * 2), CornerRadius * 2, CornerRadius * 2, 90, 90);
                Path.AddLine(XPosition, YPosition + Height - (CornerRadius * 2), XPosition, YPosition + CornerRadius);
                Path.AddArc(XPosition, YPosition, CornerRadius * 2, CornerRadius * 2, 180, 90);

                Path.CloseFigure();
                NewGraphics.DrawPath(BoxPen, Path);
           }
       }
   }
   return NewBitmap;
}

Answer 1

public static GraphicsPath RoundedRect(Rectangle bounds, int radius)
{
    int diameter = radius * 2;
    Size size = new Size(diameter, diameter);
    Rectangle arc = new Rectangle(bounds.Location, size);
    GraphicsPath path = new GraphicsPath();

    if (radius == 0)
    {
        path.AddRectangle(bounds);
        return path;
    }

    // top left arc  
    path.AddArc(arc, 180, 90);

    // top right arc  
    arc.X = bounds.Right - diameter;
    path.AddArc(arc, 270, 90);

    // bottom right arc  
    arc.Y = bounds.Bottom - diameter;
    path.AddArc(arc, 0, 90);

    // bottom left arc 
    arc.X = bounds.Left;
    path.AddArc(arc, 90, 90);

    path.CloseFigure();
    return path;
}

And you can make two extension methods for the Graphics type so you can use them as the usual Draw... and Fill... shape-drawing methods.

public static void DrawRoundedRectangle(this Graphics graphics, Pen pen, Rectangle bounds, int cornerRadius)
{
    if (graphics == null)
        throw new ArgumentNullException(nameof(graphics));
    if (pen == null)
        throw new ArgumentNullException(nameof(pen));

    using (GraphicsPath path = RoundedRect(bounds, cornerRadius))
    {
        graphics.DrawPath(pen, path);
    }
}

public static void FillRoundedRectangle(this Graphics graphics, Brush brush, Rectangle bounds, int cornerRadius)
{
    if (graphics == null)
        throw new ArgumentNullException(nameof(graphics));
    if (brush == null)
        throw new ArgumentNullException(nameof(brush));

    using(GraphicsPath path = RoundedRect(bounds, cornerRadius))
    {
        graphics.FillPath(brush, path);
    }
}

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Update 2020:

Recently I made my drawing libraries publicly available (NuGet). Feel free to explore the GraphicsExtensions class for more overloads (custom corner radius for each corners), and for other goodies.