How to read and access BootStrap CSS class for a TextBox in ASP.Net

I have converted bootstrap textbox into asp.net textbox and I want to access it in my cs i.e code behind file but i am not able to access it..please provide me appropriate solution.

 <input type="email" id="inputEmail" class="form-control" placeholder="Email " required autofocus>
 

<asp:TextBox ID="txtEmail" runat="server" CssClass="form-control" placeholder="Email"></asp:TextBox>