Core Plot - How to make a Floating Axis

Hi everyone,

I'm trying to do a XYGraph for an iOS application using the CorePlot component but I can't manage to make an axis Floating. What I want is keeping the axis line always at the same position when the user touches and drags the screen.

I've got this code.

        var axisSet = (CPTXYAxisSet) graph.AxisSet;

        // Label x with a fixed interval policy
        var x = axisSet.XAxis;
        x.LabelingPolicy = CPTAxisLabelingPolicy.Automatic;
        x.MinorTicksPerInterval = 4;
        x.PreferredNumberOfMajorTicks = 8;
        x.MajorGridLineStyle = major;
        x.MinorGridLineStyle = minor;
        x.Title = "X Axis";
        x.TitleOffset = 25f;

        // Label y with an automatic label policy. 
        var y = axisSet.YAxis;
        y.LabelingPolicy = CPTAxisLabelingPolicy.Automatic;
        y.MinorTicksPerInterval = 4;
        y.PreferredNumberOfMajorTicks = 8;
        y.MajorGridLineStyle = major;
        y.MinorGridLineStyle = minor;
        y.LabelOffset = -6f;
        y.Title = "Weight";
        y.TitleOffset = -30f;

        //Make the Y axis start on number 40
        x.OrthogonalCoordinateDecimal = NSDecimalNumber.FromFloat(40.0f).NSDecimalValue;
        plotspace.GetPlotRange (CPTCoordinate.X).Location = NSDecimalNumber.FromFloat(40.0f).NSDecimalValue;

        //Format the Y axis sufix " Kg"
        NSNumberFormatter newFormatter = new NSNumberFormatter();
        newFormatter.MinimumIntegerDigits = 1;
        newFormatter.PositiveSuffix = " Kg";
        y.LabelFormatter = newFormatter;

And the graph is shown properly like this.

but when the user scrolls to the up-right the axis are not visible

Now I want to make the axis always visible. I've found some Objective-C examples that use the instruction:

y.axisConstraints = [CPTConstraints constraintWithLowerOffset:0.0]; But I can't find the "axisConstraints" property in a CPTXYAxis object.

I've also tried with the instruction x.IsFloatingAxis = true; but it makes the app to crash.

If anyone could help me to show floating axis I would be very pleased. Thank you in advance.