Check out example codes for "mvc 5 required field validation not working". It will help you in understanding the concepts better.

Code Example 1

//1. Get JQuery validation scripts via NuGet
//PM> install-package Microsot.JQuery.Unobtrusive.Validation
//2. Add .js reference to master page (_Layout.cshtml)
<script src="/Scripts/jquery.validate.js"></script>
<script src="/Scripts/jquery.validate.unobtrusive.js"></script>

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