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While dragging the segment, the delta value (e.Delta) in DragDelta event remains zero. We have considered this as an issue.
However this can be resolved by manually calculating the delta value, using the arguments BaseYValue and NewYValue in XYSegmentDragEventArgs (i.e., difference between base value and new value). We have prepared the sample based on your requirement and please download the sample in the below location.
Also we request you to create an incident in direct trac support so that we could assist you in providing custom patch for the above mentioned issue.
Please let us know, if you need any further assistance on this.
Thanks for the update.
Please let us know if you require further assistance on this.