务必请先注意这2点：
1.
要在<head></head>里面引用js ，否则没有验证图片出来
<script src="~/Scripts/jquery-1.8.2.min.js"></script>
2.
<img id="GL_StandardCode" style="cursor: pointer;" src="@Url.Action("GetImg", "ValidateCode")[email protected]" title="看不清，点击换一张" />
//<img>标签要放在<script></script>标签的上面，否则无刷新功能
<script type="text/javascript">
$("#GL_StandardCode").click(function () {
var newSrc = "@Url.Action("GetImg", "ValidateCode")" + "?t=" + (new Date()).getTime();
this.src=newSrc;
return false;
});
</script>
3.附上别人写的验证码连接：https://www.cnblogs.com/xiaomaoau/p/9132183.html