Hi Olivier,
Thanks for choosing Syncfusion Products.
Application.Save command is binded in the chart control to save the chart.If the chart is focused, save function which is defined in the chart assembly is called instead of the user defined function. To avoid this ,please cancel the function calling by setting the e.Handle value to true in previewMouseDown event of the chart control.
Please find the attached sample.
Let me know if you have any questions.
Thanks,
Poorani
ChartPictureSaveDialog_5b3c5661.zip