how to bind dynamically dropdown based checkbox true in ng-repeat using angulrajs

hi all i am using angularjs ng-repeat i have checkbox and dropdown in inside the repeat now my need is when check the checkbox value i want bind the dropdown but now when i check the checkbox all dropdown values are changed but my need i want bind the dropdown based checkbox help how to solve

ng-repeat code

 <div ng-repeat="BFMaterialStream in BFMaterialStreams">
   <input type="checkbox" ng-change="checkchange(BFMaterialStream.MaterialStream,$index)"
   ng-model="selection.ids[BFMaterialStream.MaterialStream]" name="group" id="BFMaterialStream.MaterialStream" />
     
        <select id="MaterialElevator" tabindex="7" required typeof="text" name="Elevator"
         form="DistanceMatrixFormId" class="form-control" 
          ng-model="ViewGetBUMaterialStream.ToElevator"
     >
     <option value=''>Select</option>
     <option ng-repeat="ViewGetBUMaterialStream in ViewGetBUMaterialStreams "
      value=""
      >
     
    </option>
     </select>
       </div>

check change time bind code

$scope.checkchange=function(Stream,index){

                  $http.get('/ViewGetBUMaterialStream/' + Stream ).then(function (response) {
                        $scope.ViewGetBUMaterialStreams = response.data;
                  });

}