Hi Experts,
I am getting the below error while binding the Json data to the dropdown

and below is the code which we have in XML
<ComboBox id="combo" items="{ path: '/Form', sorter: { path: 'firstname' } }">
<core:Item key="{firstname}" text="{firstname}" />
</ComboBox>
Can somebody tell where i am doing the mistake ? and help me to resolve the issue.
KR,
Anil