index.html
 <link href="resources/css/bootstrap.min.css" rel="stylesheet">
    <link href="resources/css/bootstrap-select.css" rel="stylesheet">
    <!-- Bootstrap Core CSS -->

    <script src="resources/js/jquery-2.1.1.min.js"></script>
    <script src="resources/js/jquery-1.11.0.js"></script>

    <script src="resources/js/bootstrap-select.js"></script>

    <script src="resources/library/angular.js"></script>
    <script src="resources/library/angular-route.js"></script>
    <script src="resources/js/MainController.js"></script>
    <script src="resources/js/main-app.js"></script>

    partialview.html
    -------------------
     <select class="selectpicker" multiple ng-model="selE">
                    <option ng-repeat="e in ee">{{e}}</option>
                </select>

    <script>
    $(document).ready(function () {

        $('select').selectpicker({
            style: 'btn-default',
            size: false
        });

    });

</script>

<select class="selectpicker"
        multiple
        title='Choose one of the following...'>
  <option>Mustard</option>
  <option>Ketchup</option>
  <option>Relish</option>
</select>

angular.module('demo')
  .directive('selectpicker', function () {
    return {
      restrict: 'C',
      link: function (scope, element) {
        $(element).selectpicker({
          style: 'btn-default',
          size: false
        });
      }
    };
  });

angular.module('demo')
  .directive('selectpicker', function () {
    return {
      restrict: 'C',
      require: 'ngModel',
      link: function (scope, element, attrs, ngModel) {
        var $el = $(element);
        $el.selectpicker({
          style: 'btn-default',
          size: false
        });
        $el.on('change', function (ee, aa) {
          ngModel.$setViewValue($el.val());
          scope.$apply();
        });
      }
    };
  });

angular.module('demo')
  .controller('MainCtrl', function ($scope) {
    $scope.selected = [];
  });

<select ng-model="selected"
        class="selectpicker"
        multiple
        title='Choose one of the following...'>
  <option>Mustard</option>
  <option>Ketchup</option>
  <option>Relish</option>
</select>

<select ng-model="selected"
        class="selectpicker"
        multiple
        title='Choose one of the following...'>
  <option>Mustard</option>
  <option>Ketchup</option>
  <option>Relish</option>
</select>

angular.module('demo')
  .directive('selectpicker', function ($timeout) {
    return {
      restrict: 'C',
      require: 'ngModel',
      replace: true,
        template: '<select multiple><option ng-repeat="opt in options">{{ opt }}</option></select>',
      scope: {
        options: '='
      },
      link: function (scope, element, attrs, ngModel) {
        var $el = $(element);
        $timeout(function () {
          $el.selectpicker({
            style: 'btn-default',
            size: false
          });
        });
        $el.on('change', function (ee, aa) {
          ngModel.$setViewValue($el.val());
          scope.$apply();
        });
      }
    };
  });

<div ng-model="selected"
        class="selectpicker"
        options="issues"
        title='Choose one of the following...'>
</div>