When I add or modify an item in my dataProvider, why doesn't it show up in my DataGrid

Question :When I add or modify an item in my dataProvider, why doesn't it show up in my DataGrid?
Answer :Low-level methods like Array.push() or myArray[0] = "whatever" do not cause the
dataProvider's modelChanged event to fire.
When you work with a dataProvider, it is always best to use the dataProvider API. In the above
example, you might code: myDataProvider.addItem(myItemObject) to add an item or use
editField() to modify a value programmatically.
Alternatively, you can call myDataProvider.modelChanged yourself or reassign dataProvider to
the control, as follows: myDataGrid.dataProvider = myDataProvider;