The main idea of this approach is to interchange a value of a custom field between the "dragged" and "dropped" resources.
An approach to sort (reorder) resources based on a custom field value was demonstrated in the following example:
How to sort resources
To build a solution demonstrated in this sample into an existing application, copy the "DragDropResourcesHelper" module and pass a current SchedulerControl instance and the "sort" field name into the DragDropResourcesHelper class constructor:
[C#]DragDropResourcesHelperhelper=newDragDropResourcesHelper(schedulerControl1,"SortOrder");
[VB.NET]Dim helper AsNew DragDropResourcesHelper(schedulerControl1, "SortOrder")