How to Submit on dropdown option select

Hi,

I have an editable grid in which I have column with dropdown in it. I am trying to call submit to update values in selected row. I have been able to select single row in a rule input variable where when I change any value from dropdown the value gets changes. The issue I am facing is to insert that updated row in DB. 

Please suggest.

a!dropdownField(
                        label: "Assigned To",
                        labelPosition: "ABOVE",
                        placeholder: fv!item.assignedTo,
                        choiceLabels: {
                          "Anil Verma",
                          "Amit Singh",
                          "Gaurav Singh",
                          "Praveen Kumar",
                          "Sumit Mehta"
                        },
                        choiceValues: {
                          "Anil Verma",
                          "Amit Singh",
                          "Gaurav Singh",
                          "Praveen Kumar",
                          "Sumit Mehta"
                        },
                        saveInto: ri!rwmActivity.assignedTo,
                        searchDisplay: "ON",
                        disabled: local!editAssignedToField,
                        validations: {}
                      )

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