防止在回发ASP.Net按钮时关闭模式弹出(引导)窗口

window.onbeforeunload = function() {
    return "确定要离开吗？";
};

PostBackOptions options = new PostBackOptions(btnSubmit);
options.TrackFocus = true;
btnSubmit.Attributes.Add("onclick", Page.ClientScript.GetPostBackEventReference(options));

<div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
    <div class="modal-dialog" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h4 class="modal-title" id="myModalLabel">模态窗口标题</h4>
            </div>
            <div class="modal-body">
                <!-- 模态窗口内容 -->
            </div>
            <div class="modal-footer">
                <button type="button" class="btn btn-default" data-dismiss="modal">关闭</button>
                <button type="button" class="btn btn-primary">保存</button>
            </div>
        </div>
    </div>
</div>

$('#myModal').modal('show');