如果使用ajax在ASP.net MVC中已存在电子邮件，如何防止表单提交

I have a registration form in asp.net mvc and i want to prevent that form from submission if that particular email already exist. I want to solve it using ajax, without using Remote Attribute. Below is the code. I have checked email availability using ajax but do not know how to prevent the form submission. If user presses on the submit button then only alert box should display is email already exist.I have a registration form in asp.net mvc and i