Sometime the Gantt Table is not redraw correctly when used as Object Linking and Embedding (OLE) custom control.
How to force the Gantt Table to repaint when hidding a third party window that was covering it?
The Gantt Table is not properly redrawn or is grayed out when closing a third party window (for instance Windows Explorer) that is on top of your embedded Gantt for .NET control.
Moving the Gantt application to force a redraw solves the issue.
This issue occurrence is very low. It has been associated to the use of the BorderStyle.Fixed3D on the Gantt Table.
Resolving the problem
To avoid this issue, you need to change the BorderStyle being applied on the GanttTable
table = ganttChart.GanttTable;
table.BorderStyle = BorderStyle.FixedSingle;