Why update panel not working in bootstarp model

Quote:

<button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>

Change Password

<asp:UpdatePanel ID="updatepanel1" runat="server">
<contenttemplate>
<!-- The form is placed inside the body of modal -->

<%-- <label class="col-xs-3 control-label">Username</label>--%>
<asp:Label runat="server" AssociatedControlID="txtpassword" class="col-xs-5 control-label" ValidationGroup="register">Current Password*

<asp:TextBox ID="txtpassword" runat="server" placeholder="" class="form-control input-sm" TextMode="Password" ValidationGroup="register">

<asp:Label runat="server" AssociatedControlID="txtnewpassword" class="col-xs-5 control-label" ValidationGroup="register">New Password*

<asp:TextBox ID="txtnewpassword" runat="server" placeholder="" class="form-control input-sm" TextMode="Password" ValidationGroup="register">

<asp:Label ID="lblpassword" runat="server" CssClass="text-danger" ValidationGroup="register" Display="Dynamic" >
<asp:RequiredFieldValidator runat="server" ControlToValidate="txtnewpassword" CssClass="text-danger" ErrorMessage="Please enter passowrd" ValidationGroup="register" Display="Dynamic" />
<asp:RegularExpressionValidator ID="RegularExpressionValidator5" CssClass="text-danger" ControlToValidate="txtnewpassword" runat="server" ErrorMessage="Your password should have minimum 6 characters with 1 digit and 1 special characters" ValidationExpression="^(?=.*[A-Za-z])(?=.*\d)(?=.*[$@$!%*#?&])[A-Za-z\d$@$!%*#?&]{6,10}$" Display="Dynamic">

<asp:Label runat="server" AssociatedControlID="txtconfpassword" class="col-xs-5 control-label" ValidationGroup="register">Confirm New Password*

<asp:TextBox ID="txtconfpassword" runat="server" placeholder="" class="form-control input-sm" TextMode="Password" ValidationGroup="register">

<asp:Label ID="lblconfpassword" runat="server" CssClass="text-danger" ValidationGroup="register" Display="Dynamic" >
<asp:RequiredFieldValidator runat="server" ControlToValidate="txtconfpassword" CssClass="text-danger" ErrorMessage="Please re-enter passowrd" ValidationGroup="register" Display="Dynamic" />
<asp:CompareValidator id="comparePasswords" runat="server" ControlToCompare="txtnewpassword" CssClass="text-danger" ControlToValidate="txtconfpassword" ErrorMessage="Your password do not match up" Display="Dynamic" />

<asp:Button ID="btnchangepwd" runat="server" Text="Save Changes" CssClass="btn btn-primary btn-color btn-md" OnClick="btnchangepwd_Click" />

<triggers> <asp:AsyncPostBackTrigger ControlID="btnchangepwd" EventName="Click" />