Hi,

It seems the control does not expect ClearAll to be called from BoxCreated, and uses the reference of the just created-box after the event. You could work around that by deleting the items as follows:

private void fc_BoxCreated(object sender, MindFusion.FlowChartX.BoxEventArgs e)
{
while (fc.Boxes.Count > 0)
fc.DeleteObject(fc.Boxes[0]);
}

DeleteObject sets a flag that makes the flowchart MouseUp handler exit immediately after raising BoxCreated, which prevents using the reference to the deleted box.

Stoyan