selectAllReturns: grid

    
 <button id="btnSelectAll" class="gj-button-md">Select All</button>
 <br/><br/>
 <table id="grid"></table>
 <script>
     var grid = $('#grid').grid({
         dataSource: '/Players/Get',
         columns: [ { field: 'ID', width: 56 }, { field: 'Name' }, { field: 'PlaceOfBirth' } ],
         selectionMethod: 'checkbox',
         selectionType: 'multiple'
     });
     $('#btnSelectAll').on('click', function () {
         grid.selectAll();
     });
 </script>