Control for selecting month

Hi Pascal,
Thank you for providing additional information. I now understand the functionality you wish to achieve.
Yes, the only way to accomplish this task is to write a descendant of the DateEdit class.
First, you should write a descendant of the VistaDateEditCalendar class and override its OnItemClick method in order to close the editor's popup form when clicking a month cell. Please also override the Init method and set the View property value to DateEditCalendarViewType.YearInfo:

C#
public class MyVistaDateEditCalendar : VistaDateEditCalendar  
   {  
       public MyVistaDateEditCalendar(RepositoryItemDateEdit item, object editDate) : base(item, editDate) { }  

       protected override void Init()  
       {  
           base.Init();  
           this.View = DateEditCalendarViewType.YearInfo;  
       }  

       public override void OnItemClick(DevExpress.XtraEditors.Calendar.CalendarHitInfo hitInfo)  
       {  
           DayNumberCellInfo cell = hitInfo.HitObject as DayNumberCellInfo;  
           if (View == DateEditCalendarViewType.YearInfo)  
           {  
               DateTime dt = new DateTime(DateTime.Year, cell.Date.Month, CorrectDay(DateTime.Year, cell.Date.Month, DateTime.Day), DateTime.Hour, DateTime.Minute, DateTime.Second);  
               OnDateTimeCommit(dt, false);  
           }  
           else  
               base.OnItemClick(hitInfo);  
       }  
   }  

Then, it is required to write a custom PopupDateEditForm, and override its CreateCalendar method in order to use this kind of calendar:

C#
public class MyVistaPopupDateEditForm : VistaPopupDateEditForm  
   {  
       public MyVistaPopupDateEditForm(DateEdit ownerEdit) : base(ownerEdit) { }  
       protected override DateEditCalendar CreateCalendar() {  
           return new MyVistaDateEditCalendar(OwnerEdit.Properties, OwnerEdit.EditValue);  
       }  
   }  

Finally, please write a descendant of the DateEdit class and override its CreatePopupForm method:

C#
public class MyDateEdit : DateEdit  
{  
    protected override PopupBaseForm CreatePopupForm()  
    {  
        if (Properties.VistaDisplayMode == DevExpress.Utils.DefaultBoolean.True)  
            return new MyVistaPopupDateEditForm(this);  
        return new PopupDateEditForm(this);  
    }  
}  

I believe this information will be of some help. Please keep us informed of your progress.
Thanks,
Vito