This is a Star Rating Control implementation for C# WinForms that has been derived from here, the original article has a broken link for the source code of the custom control, this repository is a rebuild of the linked custom control, with some other extra changes.
As per the author stated, this custom control can be optimized by caching some values to optimize performance. This reimplementation applies that idea by caching data points using arrays. The render data for the stars will only be redrawn when any of the fields that are part of the rendering process (such as the margin, and star count) has been changed. Otherwise, calling Invalidate() will simply recolor the stars, making the OnMouseMove() and other methods to be at least somewhat faster.
As per the author, the custom control could also benefit from extra exposed brush style properties, which this reimplementation also does. The new properties are FillBrushStyle, StarColor, and GradientDirection. The FillBrushStyle can either be Solid or Gradient. The GradientDirection determines the gradient color direction application (if I described it correctly, which indicates on what direction should the first color fade to the second color), and the StarColor determines the color of the stars themselves, which is used on GradientDirection to apply the gradient color.
This reimplementation also provides an OnMouseDown() event to allow clicking of the stars, as well as the SelectedStar property, which is used to retrieve the value of the current selected star.
Some other changes here includes using SmoothingMode.AntiAlias to reduce jagged lines, and allowing for a proper distinction between selected and unselected stars during mouse hover, by coloring unselected stars with the HoverStarColor, and selected stars with SelectedStarColor