Hello Nazha,

It has been a while since you have made your post, in case you still need support I will be glad to assist you further. I suppose the other community members can benefit from this answer as well. I have been looking into your post and since the DatePicker is a Microsoft’s controls I cannot be completely sure how you can achieve the functionality you want. Although I find the following forum thread from Stackoverflow:

http://stackoverflow.com/questions/1798513/wpf-toolkit-datepicker-month-year-only

where a similar question like yours is discussed and a solution is provided.

Feel free to write me if you have further questions.