C# Signature:

[DllImport("gdi32.dll")]
static extern bool RoundRect(IntPtr hdc, int nLeftRect, int nTopRect,
   int nRightRect, int nBottomRect, int nWidth, int nHeight);

User-Defined Types:

None.

Notes:

None.

Tips & Tricks:

Please add some!

Sample Code:

public class GDI32
{
    #region GDI32 Functions
    [DllImport("gdi32.dll")]
    public static extern bool RoundRect(RECT lpRect, Point point);

    [DllImport("gdi32.dll")]
    public static extern bool RoundRect(IntPtr hdc, int nLeftRect, int nTopRect,
    int nRightRect, int nBottomRect, int nWidth, int nHeight);

    [DllImport("gdi32.dll")]
    public static extern IntPtr CreateSolidBrush(uint crColor);

    [DllImport("gdi32.dll")]
    public static extern IntPtr CreatePen(int fnPenStyle, int nWidth, uint crColor);

    [DllImport("gdi32.dll")]
    public static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);

    [DllImport("gdi32.dll")]
    public static extern bool DeleteObject(IntPtr hObject);

    public static int RGB(Color color)
public class GDI32
    {
        return color.ToArgb() & 0xffffff;
    }
        #region GDI32 Functions
        [DllImport("gdi32.dll")]
        public static extern bool RoundRect(RECT lpRect, Point point);

    #endregion
}
        [DllImport("gdi32.dll")]
        public static extern bool RoundRect(IntPtr hdc, int nLeftRect, int nTopRect,
            int nRightRect, int nBottomRect, int nWidth, int nHeight);

public class RoundControl : System.Windows.Forms.Control
{
    protected override void OnPaint(PaintEventArgs e)
    {
        DrawRoundRect(e.Graphics);
    }
        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateSolidBrush(uint crColor);

    public void DrawRoundRect(Graphics gr)
    {            
        RECT rect = new RECT(0, 0, this.Width, this.Height);
        IntPtr hDC = gr.GetHdc();
        IntPtr thePen = GDI32.CreatePen(0, 1, (uint)GDI32.RGB(Color.White));
        IntPtr theBrush = GDI32.CreateSolidBrush((uint)GDI32.RGB(Color.White));
        IntPtr oldPen = GDI32.SelectObject(hDC, thePen);
        IntPtr oldBrush = GDI32.SelectObject(hDC, theBrush);        
        [DllImport("gdi32.dll")]
        public static extern IntPtr CreatePen(int fnPenStyle, int nWidth, uint crColor);

        GDI32.RoundRect(hDC, 0, 0, this.Width, this.Height, 20, 20);
        [DllImport("gdi32.dll")]
        public static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);

        GDI32.SelectObject(hDC, oldPen);
        GDI32.DeleteObject(thePen);
        GDI32.SelectObject(hDC, oldBrush);            
        GDI32.DeleteObject(theBrush);
        [DllImport("gdi32.dll")]
        public static extern bool DeleteObject(IntPtr hObject);

        gr.ReleaseHdc(hDC);            
    }
}
        public static int RGB(Color color)
        {

/*

            byte [] RGBCOLORS = new byte [4];
            RGBCOLORS[0] = color.R;
            RGBCOLORS[1] = color.G;
            RGBCOLORS[2] = color.B;
            RGBCOLORS[3] = 0;
            return BitConverter.ToInt32(RGBCOLORS, 0);

*/

            return color.ToArgb() & 0xffffff;
        }

Alternative Managed API:

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        #endregion
    }

public class RoundControl : System.Windows.Forms.Control
{
    protected override void OnPaint(PaintEventArgs e)
    {
         DrawRoundRect(e.Graphics)
    }

    public void DrawRoundRect(Graphics gr)
        {            
            RECT rect = new RECT(0, 0, this.Width, this.Height);
            IntPtr hDC = gr.GetHdc();
            IntPtr thePen = GDI32.CreatePen(0, 1, (uint)GDI32.RGB(Color.White));
            IntPtr theBrush = GDI32.CreateSolidBrush((uint)GDI32.RGB(Color.White));
            IntPtr oldPen = GDI32.SelectObject(hDC, thePen);
            IntPtr oldBrush = GDI32.SelectObject(hDC, theBrush);        

            GDI32.RoundRect(hDC, 0, 0, this.Width, this.Height, 20, 20);

            GDI32.SelectObject(hDC, oldPen);
            GDI32.DeleteObject(thePen);
            GDI32.SelectObject(hDC, oldBrush);            
            GDI32.DeleteObject(theBrush);

            gr.ReleaseHdc(hDC);            
        }
}

Alternative Managed API:

Do you know one? Please contribute it!

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