Attaching expected result screeshot
Hello Lalit,
Thank you for your post.
I have been looking into your requirements and what I can suggest to you if you want to delete the existing ‘Custom’ FilterDropDownItem is to handle the RecordFilterDropDownPopulating event of XamDataGrid. In the event handler you can find the DropDownItem you want and remove it by using the Remove method of DropdownItems collection. I created a short project in order to show you how you can implement this approach.
Currently our XamDataGrid control does not provide the ability for multiple selection of ComboBoxItems in the filter ComboBox. What I can suggest is to use the Excel Style Record Filtering. You can read more details from the following link from our online documentation: http://help.infragistics.com/doc/WPF/2015.1/CLR4.0/?page=xamDataPresenter_Enable_ExcelStyle_Record_Filtering.html