WYSIWYG Progress Circle for .NET Framework (C#)

 private System.Collections.Generic.Dictionary<Color, SolidBrush> _brushCache = 
            new System.Collections.Generic.Dictionary<Color,SolidBrush>();

		private void DrawFilledArc (Graphics grp, Color color, int startAngle)
		{
			grp.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

			Rectangle main = this.ClientRectangle;
			
			// If there is no region to be drawn, then this method terminates itself
			if (main.Width - (2*this._ringThickness) < 1 || main.Height -(2*this._ringThickness) <= 1)
				return;

			// Calculates the region that will be filled

            using (GraphicsPath outerPath = new GraphicsPath())
            {
                outerPath.AddPie(main, startAngle, this.PieAngle);

                Rectangle sub = new Rectangle(main.X + this._ringThickness, main.Y + this._ringThickness, main.Width - (2 * this._ringThickness), main.Height - (2 * this._ringThickness));

                using (GraphicsPath innerPath = new GraphicsPath())
                {
                    innerPath.AddPie(sub, startAngle - 1, this.PieAngle + 2);

                    using (System.Drawing.Region mainRegion = new Region(outerPath))
                    {
                        using (System.Drawing.Region subRegion = new Region(innerPath))
                        {

                            mainRegion.Exclude(subRegion);
                            
                            SolidBrush targetBrush;
                            
                            if (_brushCache.ContainsKey(color))
                            {
                                targetBrush = _brushCache[color];
                            }
                            else
                            {
                                targetBrush = new SolidBrush(color);
                                _brushCache.Add(color,targetBrush);
                            }
                            // Fill that region
                            grp.FillRegion(targetBrush, mainRegion);
                        }
                    }
                }
            }
		}