Use the GDI library objects to draw rectangles that have rounded rectangles of a specified radius. The secret is to use a series of lines and arcs to form the rectangle as desired.

public void DrawRoundRect(Graphics g, Pen p, float x, float y, float width, float height, float radius)
{
    GraphicsPath gp = new GraphicsPath();

    gp.AddLine(x + radius, y, x + width - (radius * 2), y); // Line
    gp.AddArc(x + width - (radius * 2), y, radius * 2, radius * 2, 270, 90); // Corner
    gp.AddLine(x + width, y + radius, x + width, y + height - (radius * 2)); // Line
    gp.AddArc(x + width - (radius * 2), y + height - (radius * 2), radius * 2, radius * 2, 0, 90); // Corner
    gp.AddLine(x + width - (radius * 2), y + height, x + radius, y + height); // Line
    gp.AddArc(x, y + height - (radius * 2), radius * 2, radius * 2, 90, 90); // Corner
    gp.AddLine(x, y + height - (radius * 2), x, y + radius); // Line
    gp.AddArc(x, y, radius * 2, radius * 2, 180, 90); // Corner
    gp.CloseFigure();

    g.DrawPath(p, gp);
    gp.Dispose();
}

Explanation:

This method, DrawRoundRect, is designed to draw a rectangle with rounded corners on a graphical interface using GDI+ in C#. It takes parameters for positioning, size, and styling:

• Graphics g: The graphics context on which the rectangle will be drawn.
• Pen p: The pen used for drawing the outline of the rectangle.
• float x, float y: The coordinates for the top-left corner of the rectangle.
• float width, float height: The dimensions of the rectangle.
• float radius: The radius of the rounded corners.

The method constructs a GraphicsPath object (gp) to define the shape of the rectangle:

1. Straight Lines (gp.AddLine): These lines create the top, bottom, and sides of the rectangle, connecting the arcs that form the rounded corners.
2. Arcs for Corners (gp.AddArc): These arcs create the rounded corners. Each AddArc call draws a quarter-circle. The parameters define the bounding rectangle for the arc, the start angle, and the sweep angle (in degrees).
3. Closing the Path (gp.CloseFigure): This ensures that the last point of the path connects back to the first point, creating a closed shape.

After defining the path, the method:

• Uses g.DrawPath(p, gp) to draw the path on the Graphics object g using the Pen p.
• Disposes of the GraphicsPath object with gp.Dispose() to free resources.

The method is useful for drawing custom shapes with smooth, rounded corners in GUI applications, providing a more visually appealing alternative to sharp-cornered rectangles.