how to save previous selected value of dropdown in local variables?

a!localVariables(
  local!dropdownValue:{"A","B","C","D"},
  local!selected,
  local!existingSelection,

  local!isSectionRefresh: if(local!selected="D", true(),
  if(and(local!selected="A",
  index(local!existingSelection,(count(local!existingSelection)-1),"")="D"),true(),
  false()
  )
  ),
  
  {
    a!dropdownField(
      label:"Dropdown",
      choiceLabels: local!dropdownValue,
      choiceValues: local!dropdownValue,
      placeholder: "Please select",
      value: local!selected,
      saveInto: {
        local!selected,
        a!save(local!existingSelection,
        append(local!existingSelection,local!selected))
      }
    ),
    a!textField(
      label:local!existingSelection,
      value: if(local!isSectionRefresh, null, local!selected)
     
    )
  }
)

You can try something similar to this

thank u ankitab254

The above posted code will work (though i'm unclear what "should be refreshed" really implies from your initial requirement description); however I'd personally recommend simplifying if possible and just using stacked saveIntos to save a single "last value" historical copy whenever the dropdown is changed.  You can then (i assume) store your logic for the "refresh" condition in a subsequent local variable, which will refresh anytime either of the earlier values gets changed.

a!localVariables(
  local!values: { "A", "B", "C", "D" },
  local!currentSelection,
  local!oldSelection,

  local!isRefresh: if(
    isnull(local!oldSelection),
    "",
    "" /* put refresh logic here */
  ),

  {
    a!dropdownField(
      label: "Dropdown",
      choiceLabels: local!values,
      choiceValues: local!values,
      placeholder: "--select a value--",
      value: local!currentSelection,
      saveInto: {
        a!save(
          local!oldSelection,
          local!currentSelection
        ),
        a!save(
          local!currentSelection,
          save!value
        )
      }
    )
  }
)

thank u Mike Schmitt