Draw Rounded Corner Rectangles Using C#

Draw Rounded Corner Rectangles Using C#
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

    g.DrawPath(p, gp);


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.

Nathan Pakovskie is an esteemed senior developer and educator in the tech community, best known for his contributions to Geekpedia.com. With a passion for coding and a knack for simplifying complex tech concepts, Nathan has authored several popular tutorials on C# programming, ranging from basic operations to advanced coding techniques. His articles, often characterized by clarity and precision, serve as invaluable resources for both novice and experienced programmers. Beyond his technical expertise, Nathan is an advocate for continuous learning and enjoys exploring emerging technologies in AI and software development. When he’s not coding or writing, Nathan engages in mentoring upcoming developers, emphasizing the importance of both technical skills and creative problem-solving in the ever-evolving world of technology. Specialties: C# Programming, Technical Writing, Software Development, AI Technologies, Educational Outreach

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