Hi Olivier Vayssie,
Thanks for choosing Syncfusion products.
By default if you bind the string value content to the BindingPathX property of Chart series then you can directly use the "DataPoint.Tag" for Adornment label content.
If you bind the double value content to the BindingPathX property then you can initialize adornment label content by using "DataPoint.Tag.PropertyName".
Where as here you are using the DataTable object for Chart series DataSource. So you can initialize by using the following way.
C#:
this.Chart1.Areas[0].Series[0].AdornmentsInfo.LabelContentPath = "DataPoint.Tag.ItemArray[1]";
We made some changes in your sample to achieve your requirement. Please find the attached sample from the below location for more information.
http://help.syncfusion.com/support/Chart.WPF/7.4.0.20/F91890/main.htmLet us know if you have any questions.
Thanks & Regards,
Murugavel P