Am I missing something here, or why don't you just set the MarkerTooltipMode to MarkerTooltipMode.Never when you want to hide the Tooltip?
Here's the relevant code:
/// <summary>
/// modeof tooltip
/// </summary>
public enum MarkerTooltipMode
{
OnMouseOver,
Never,
Always,
}
// tooltips above
foreach(GMapMarker m in Markers)
{
//if(m.ToolTip != null && m.IsVisible && Control.Core.currentRegion.Contains(m.LocalPosition.X, m.LocalPosition.Y))
if(m.ToolTip != null && m.IsVisible)
{
if(!string.IsNullOrEmpty(m.ToolTipText) && (m.ToolTipMode == MarkerTooltipMode.Always || (m.ToolTipMode == MarkerTooltipMode.OnMouseOver && m.IsMouseOver)))
{
m.ToolTip.OnRender(g);
}
}
}