[Chart] Updating ActrualMaximum from viewModel does not work!!

I got an example from another thread "http://www.mindscapehq.com/forums/thread/4818" to make strip chart by updating ActualMaximum property during the chart updating. But what's different from that example is that I'm using MVVM pattern, I update ActualMaximum from my viewModel by data binding during the chart updating. But something is weird that it only works at the initialization of my chart. but not work during the line updating.
It goes like below: 1. I set ActualMaximum in the constructor method of my viewModel as a default value for the property. 2. I update ActualMaximum during the line updating process.
When I run the program, firstly the chart shows up, the default value I set in the constructor method is applied to the chart successfully. And then I start to run the line updating process, bu the x axis max value does not change at all. So firstly, is my solution reasonable to update ActualMaximum during line updating process? Or do I missing something or make any mistake? Any help will do me a great favor, Thanks!

Thanks Jason, But I've try that way already, it seems that's not the case. Below is my code snippet, maybe there is something you can find, Thanks a lot.

    <StackPanel Orientation="Vertical">
        <ms:Chart Name="theChart" Title="{Binding ChartTitle}" ZoomMode="Both" LegendStyle="{StaticResource LegendStyle}" MinHeight="500" viewsModel:CollectionBinder.SynchronizedSelectedItems="{Binding Lines}" LegendPosition="{Binding LengendPos}">
            <ms:Chart.XAxis>
                <ms:ChartAxis SliderStyle="{StaticResource MySlider}" Title="{Binding XTitle}" IsSliderVisible="{Binding SliderVisibility}" TickMarkMode="Movable" MinorTickMarkVisibility="Visible" LabelLayout="Inside"
                              Maximum="{Binding XMaxiMum, Mode=TwoWay}" ActualMaximum="{Binding XActualMaximum, Mode=TwoWay}" ActualMinimum="{Binding XActualMinimum, Mode=TwoWay}"/>
            </ms:Chart.XAxis>
            <ms:Chart.YAxis>
                <ms:ChartAxis Title="{Binding Y1Title}" LabelLayout="Inside" Background="{Binding Y1AxisColor}" Foreground="{Binding Y1AxisColor}" IsSliderVisible="{Binding SliderVisibility}" SliderStyle="{StaticResource MySlider}"/>
            </ms:Chart.YAxis>
            <ms:Chart.AlternativeYAxes>
                <ms:ChartAxis Title="{Binding Y2Title}" LabelLayout="Inside" Background="{Binding Y2AxisColor}" Foreground="{Binding Y2AxisColor}" IsSliderVisible="{Binding SliderVisibility}" SliderStyle="{StaticResource MySlider}"/>
            </ms:Chart.AlternativeYAxes>
        </ms:Chart>
        <!--<Button Name="Run_But" Content="RUN" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Command="{Binding GoGraph}" CommandParameter="{Binding ElementName=theChart}" MinHeight="25" MinWidth="100" MaxWidth="150" MaxHeight="70" Margin="5" />-->
        <!--<Button Content="Graph Setting" HorizontalAlignment="Center" VerticalAlignment="Top" Command="{Binding GoGraph}" MinHeight="25" MinWidth="100" MaxWidth="150" MaxHeight="70" Margin="15"/>-->
    </StackPanel>

The viewModel goes like below:

    public double XMaxiMum
    {
        get { return xMaxiMum; }
        set
        {
            xMaxiMum = value;
            onPropertyChanged("XMaxiMum");
        }
    }

    public double XActualMaximum
    {
        get { return xActualMaximum; }
        set
        {
            xActualMaximum = value;
            onPropertyChanged("XActualMaximum");
            System.Diagnostics.Debug.WriteLine("***********:" + xActualMaximum.ToString());
        }
    }

    public double XActualMinimum
    {
        get { return xActualMinimum; }
        set
        {
            xActualMinimum = value;
            onPropertyChanged("XActualMinimum");
        }
    }

And below is the snippet of updating ActualMaximum property, it's following your example of strip chart:

    private void adjustWindow()
    {
        int xcolIndex = -1;
        foreach (LineSeries line in this.Lines)
        {
            System.Diagnostics.Debug.WriteLine("XBinding :" + line.XBinding.Path.Path);
            string xbing = line.XBinding.Path.Path;
            int findex = xbing.LastIndexOf("[");
            int lindex = xbing.LastIndexOf("]");
            xcolIndex = Convert.ToInt16(xbing.Substring(findex + 1, lindex - findex - 1));
            break;
        }
        if (xcolIndex == -1)
        {
            System.Diagnostics.Debug.WriteLine("Invalid xcolIndex!!! ");
        }
        double v = (double)MeasurementDataTable.Rows[MeasurementDataTable.Rows.Count - 1][xcolIndex];
        bool autoScroll = false;
        if (v > this.XActualMaximum)
        {
            autoScroll = true;
        }
        double actMax = this.XActualMaximum;
        this.XMaxiMum = Math.Max(this.window, v);
        this.XActualMaximum = actMax;
        if (autoScroll)
        {
            this.XActualMaximum = v;
            this.XActualMinimum = v - this.window;
        }
    }

Hello Yaron

To fix this, please try make your ActualMaximum property on your view model both readable and writeable (get and set). Then use a TwoWay binding when binding the axis to your ActualMaximum property.

The problem is that the axis has some internal logic that can modify the ActualMaximum property as a result of ensuring constraints or performing operations such as zooming. Unfortunately in WPF, doing this causes any bindings on the ChartAxis.ActualMaximum property to be overwritten - unless there is a TwoWay binding.

Jason Fauchelle

Thank Jason, But I've tried that way you suggested, it seems not the case. I don't know maybe I've missed some flag configuration or something else? And I've appended my code snippet, maybe you can find something. Thanks a lot.

Thanks for the code Yaron

I could not find any issues with the code you posted. Could there be an issue in your onPropertyChanged method?

I have attached an updated version of the StripCharting demo that uses an MVVM approach. The functionality all works fine. If you want to run the sample to see it working, make sure to add a reference to your copy of the Mindscape.WpfElements.dll. See if you can use this sample to find the issue in your project. Or if you can send me a full sample of what you have so far, I can investigate it for you.

Jason Fauchelle