chart.Axis.Y.RangeMin = yourMinValue;chart.Axis.Y.RangeMax = yourMaxValue;chart.Axis.Y.RangeType = RangeType.Custom;
By DataValue+50 I assume that you mean the max value that's coming from the dataset, which you then intend to round to the nearest hundred. If that's the case, you have to go through your dataset and calculate min and max yourself.