materialCheckBox has no support for the indeterminate state.
Simplest solution might be as follows:
Define a new Point array
private static readonly Point[] INDETERMINATE_LINE = { new Point(4, 9), new Point(14, 9) };
change the code drawing the check mark to support both states thus:
materialCheckBox has no support for the indeterminate state. Simplest solution might be as follows: Define a new Point array
private static readonly Point[] INDETERMINATE_LINE = { new Point(4, 9), new Point(14, 9) };
change the code drawing the check mark to support both states thus:if(CheckState == CheckState.Indeterminate) { g.DrawLines(cmpen, INDETERMINATE_LINE); } else { g.DrawLines(cmpen, CHECKMARK_LINE); }