Hi Mahdi,
Sorry for the delay in responding.
To set custom labels for the axis ChartAxisTickLabelDrawingMode must be set as Usermode. But in the code you have given as Automaticmode. So this will not force custom labels to be displyed. I have created a sample to set custom labels for the axis. Kindly get the sample from the following link.
http://files.syncfusion.com/support/Chart.Windows/V7.2.0.20/F83927/main.htmKindly, let me know if you have any other queries.
Thanks,
Manimala.