Thanks, I didn't recognize it.

I implemented that code now, but I get for the itemIndex always -2147483648

private void dataChart_MouseMove(object sender, MouseEventArgs e)
        {
            XamDataChart chart = sender as XamDataChart;
            Point mousePosition = e.GetPosition(chart.Series[0].RootCanvas);

            int itemIndex = (int)xAxis.UnscaleValue(mousePosition.X);
            Debug.Print(itemIndex.ToString());
            if (itemIndex >= 0 && itemIndex < _viewModel.ChartItems.Count)
            {
                _viewModel.CurrentToolTipTimestamp = _viewModel.ChartItems[itemIndex].Timestamp;
            }
        }

I am using a CategoryDateTimeXAxis. Can that be an issue?

<ig:XamDataChart.Axes>
                            <ig:CategoryDateTimeXAxis Name="xAxis" ItemsSource="{Binding ChartItems}" DateTimeMemberPath="Timestamp" Label="{}{0:HH:mm:ss}"
                                                      MinimumValue="{Binding XAxisMinimum}" MaximumValue="{Binding XAxisMaximum}" 
                                                      Strip="Transparent" MajorStroke="Transparent"/>

                            <ig:NumericYAxis Name="yAxis" Label="{Binding YAxisLabel}" 
                                             MinimumValue="{Binding ChartSettings.YAxisActualMinValue}"
                                             MaximumValue="{Binding ChartSettings.YAxisActualMaxValue}"/>
                        </ig:XamDataChart.Axes>

Hi Bin,

I am wondering if you have had the chance to take a closer look at the latest sample? I am asking this because, as mentioned in my previous message, there is code that serves to retrieve the index of the item under the current mouse position, so that the category name can be displayed in the tooltip as well. As I am not aware of your data model and the sample’s purpose is to demonstrate the CategoryToolTipLayer rather than specific data, the X Axis in the sample is not a Timestamp object, however the approach would be just the same.

Please, take a look at the below screenshot, where you can see that the category name “C5” for which the tooltip is currently displayed is also present in the tooltip text:

In case you need further assistance with anything specific, I could suggest modifying the sample with the relevant code and sending it back to me, so I can investigate it. If you have any other questions, please let me know.

Best regards,
Bozhidara Pachilova

Thanks for the example.

i would like to show the timestamp at the top of the tooltip. How can I access the series item?