<div class="modal fade" id="myAddModal" tabindex="-1" role="dialog">
    <div class="modal-dialog" role="document">
        <div class="modal-content">
            <form id="form_baidang" class="col-sm-12">
                    <div class="form-group col-sm-12">
                        @Html.LabelFor(model => model.Content, new { @class = "control-label" })
                        @Html.ValidationMessageFor(model => model.Content, "", new { @class = "text-danger col-sm-12" })
                        @Html.EditorFor(model => model.Content, new { htmlAttributes = new { @class = "form-control col-sm-12", } })
            </form>
        </div>
    </div>
</div>

var editor = CKEDITOR.replace('Content', {
                customConfig: '/xxx/ckeditor/config.js',
            });