Input groups are another way to provide the user with additional information about the data you expect them to enter in a specific form element. Bootstrap provides classes to add sections either before or after an input element. These sections can contain either text or an icon.
To create a text input element to indicate to the user that we require them to enter a phone number into the field, we'll use the following markup:
@model Chapter3.Models.PersonModel
<div class="container">
<div class="row">
<div class="col-md-6">
<label asp-for="Phonenumber" class="col-md-4 control-label">
</label>
<div class="input-group">
<span class="input-group-addon" id="PhoneNumber">
<i class="fa fa-phone"></i></span>
<input asp-for="Phonenumber" class="form-control"
...
