Session variable and you are redirected to the Dashboard view. Refer - CheckedComboBo圎dit - add AllowMultiSelect property devexpress thread and attached example.Your select statement is going to return a null on the union, so I am assuming you want to select that.as a work-around, try saving combobox selection in a session variable, like this:
Devexpress combobox multiple selection devexpress multi select dropdown winforms Details: The GridLookup emulates a combo box that allows end-users to select multiple items within its drop-down list in the demo.
