Hi I have had the same problem and would like it to be solved.

But for a workaround of this problem i just took the line series and put another point

of the same y value on the x value where the next point should be displayed.

Thus i created my own stairstep series out of a line series.

In code this means :

// value and time are double [ ]

for (int i = 1; i < time.Length - 1; i++)
{
if (value[i] != value[i + 1])
series.Points.Add(new DataPoint(time[i], value[i])); //set the point into the series
if (time[i + 1] != null) // if the series has more points
{
series.Points.Add(new DataPoint(time[i + 1], value[i])); // add the same y value to the pos of i+1
}
}