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IsZeroBased is a boolean property that specifies whether the axis begins from 0. If you set IsZeroBased to false and the chart has all its items with equal value there is not enough information to calculate the axis range i.e. if all the values are 5 the range might be 4-6, 3-7 or -10. Then you should set AutoScale = false and point manually Max and Min point of the Axis.
Alternatively, you can set IsZeroBased to true, because in this case Axis starts from 0 and defines automatically the highest point of your SeriesItems. In this way you will be able to draw the desirable chart with equal items.
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