Since ASP.Net changes the field name when rendering the controls, you have to use
<%= control.UniqueID %>
as the name of fields. For more information, please refer to the
official documentation.
<%@ Page
Title=""
Language="C#"
MasterPageFile="~/Master.Master"
AutoEventWireup="true"
CodeBehind="..."
Inherits="..." %>
<asp:ContentID="Content1"ContentPlaceHolderID="ContentPlaceHolder1"runat="server"><!-- Fields --><asp:TextBoxrunat="server"CssClass="form-control"ID="userNameTextBox"/><scripttype="text/javascript">$(document).ready(function(){$('#form1').formValidation({framework:'bootstrap',icon:{valid:'glyphicon glyphicon-ok',invalid:'glyphicon glyphicon-remove',validating:'glyphicon glyphicon-refresh'},fields:{// There is no single quote<%=userNameTextBox.UniqueID%>:{validators:{notEmpty:{message:'The username is required and cannot be empty'},stringLength:{min:6,max:30,message:'The username must be more than 6 and less than 30 characters long'},regexp:{regexp:/^[a-zA-Z0-9]+$/,message:'The username can only consist of alphabetical and number'},different:{field:'password',message:'The username and password cannot be the same as each other'}}}}});});</script></asp:Content>