I have a List that is SQL Based and is also using Pagination. I would like to create a button that can sort the list by two fields (Last Name and then First Name) I need to use server side sort because of the pagination and I think I can use the computeSearchFromMetaDataAndFilterList Method. The documentation says:

//Filter a List called 'LIST1' on the COUNTRY column for values 'USA', 'UK' or 'Canada'
//and sort the result in descending order by COUNTRY.
var arr = [];
var searchObject = {
searchControlValue: ['USA','UK','Canada'],
searchField: 'COUNTRY'
};
var sortObject = {
sortExpression : 'COUNTRY',
direction: 'DESC'
};
arr.push(searchObject) //you can push multiple searchObjects onto the array
arr.push(sortObject); //you can push multiple sortObjects onto the array

var searchDataJSON = JSON.stringify(arr);

var options = { } //use default values
var optionsJSON = JSON.stringify(options)

{dialog.object}.computeSearchFromMetaDataAndFilterList('LIST1',optionsJSON,searchDataJSON);
The documentation seems to indicate That I can do this "you can push multiple sortObjects onto the array"

I have tried: sortExpression: ['LAST_NAME', 'FIRST_NAME'],
but it doesn't work, Any ideas what the right syntax might be?

Thanks