Hi Rohit,
You can do as below,
- Use the ChangeEventListener of the drop down item and call a microflow.
- In microflow you can use retrieve activity (from database) and then add filter conditions. In the filter condition you can use the parameter which was took over.
- Configure the DataSource accordingly the microflow will provide the filtered data object.
you can refer this link: https://docs.mendix.com/refguide/drop-down/#events
Or you can use this marketplace widget: https://marketplace.mendix.com/link/component/49364
I hope this helps.