how to make input field required code example

Example 1: change input required text html

<input type="text" id="username" required placeholder="Enter Name"
    oninvalid="this.setCustomValidity('Enter User Name Here')"
    oninput="this.setCustomValidity('')"  />

Example 2: C# form required attribute

@Html.TextBoxFor(m => m.ShortName, 
new { @class = "form-control", placeholder = "short name", required="required"})