Validation in ASP.Net MVC4 for unbound textboxes - asp.net-mvc-4

Question

I have the following code for a view, in which I am submitting some data from 3 different text-boxes. This is just a practice sample that I created. I am using Razor syntax with MVC4 in ASP.Net.
My question: How can I validate the text-boxes so they are always required?
#{
ViewBag.Title = "HelloWorld";
Layout = "~/Views/Shared/_Layout.cshtml";
}
<h2>HelloWorld</h2>
<div>This is a sample Hello World page</div>
<h1>#ViewBag.Title</h1>
<h2>#ViewBag.Message</h2>
#using (Html.BeginForm("HandleSubmit", "Home"))
{
#Html.AntiForgeryToken()
#Html.ValidationSummary()
<fieldset>
<legend>Registration Form</legend>
<ol>
<li>
#Html.Label("username", "UserName")
#Html.TextBox("username")
</li>
<li>
#Html.Label("pwd", "Password")
#Html.Password("pwd")
</li>
<li>
#Html.Label("cpwd", "Confirm Password")
#Html.Password("cpwd")
</li>
</ol>
<input type="submit" value="TestPost" />
<div style="color:red;font-weight:bold">#ViewBag.Feedback</div>
</fieldset>
}
UPDATE 1: Another way to validate textbox and show a custom invalid message is as below.
#Html.TextBox("username", null, new { #required = "required",
#oninvalid = "this.setCustomValidity('This data is a must')" })

Answer 1

Set the required attribute in the html attributes parameter for the helper
#Html.TextBox("username", null, new { #required="required", #oninvalid="setCustomValidity('I\'m required')" })
To customize this and get the same effect as the MVC templates you need jquery.validate.js and jquery.validate.unobtrusive.js
#Html.TextBox("username", null, new { #data_val_required="I'm required", #data_val="true" })
<span data-valmsg-replace="true" data-valmsg-for="username"></span>