Our API doesn't allow that you customize the Gridlines separately from one another. What I can suggest is that you use MarkedZone
to achieve your scenario. What you'll need to do is to position the zone on the place where your 0 MajorGridLine is and set the ValueStartY and ValueEndY properties equal so that the Marked Zone appears as horizontal line. Use the border to specify the line color and style. You may refer to this forum post where a similar topic has been discussed.
All the best,
the Telerik team
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